FINAL EXAM-SMOOT MAJOR – Flashcards

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question
All living organisms share five fundamental characteristics. Which of the following is not one of these characteristics?
answer
Sexual recombination
question
Pasteur's experiment provided conclusive evidence to reject the spontaneous generation hypothesis, which states that cells arise from nonliving material. As a consequence, his results supported the all-cells-from-cells hypothesis. Which element of Pasteur's experimental design was most important and why?
answer
His two treatments differed only in the shape of the flask, resulting in exposure of only one of the treatments to preexisting cells.
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Lance Armstrong just finished third (by about 5 minutes) in the 2009 Tour de France cycling race. This was an incredible feat for the 37-year-old father of 4. First and second-place winners, Alberto Contador (age 27) and Andy Schleck (age 24), respectively, have no children. Which of these three men shows the greatest evolutionary fitness?
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Lance Armstrong, because he has reproduced
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Carl Woese et al. studied small __________molecules and established the concept of the ____________.
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rRNA; domains
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In the diagram below, "A" is _____ ; "B" is _____.
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the results of several experiments support the hypothesis.
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Which of the following statements is true about biological studies?
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Hypotheses may be tested by a combination of observation, measurement, and experimentation.
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Water has what type bonds?
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polar covalent
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How many electrons are involved in a double covalent bond?
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four
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An atom has six electrons in its valence shell. How many single covalent bonds would you expect it to form in most circumstances?
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two
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If an atom is electrically neutral, which of the following must be true?
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It has the same number of protons as electrons.
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. Which of the following is a violation of the first law of thermodynamics?
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The universe will eventually die, and it will have no energy left in it.
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Water also has several remarkable properties, largely due to its ability to form hydrogen bonds. Which property does NOT apply to water?
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All of the above are properties of water
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A pH of _____is considered neutral and a pH of ______ is acidic.
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7;3
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The energy of movement is called __________ and produces an_______________ reaction.
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kinetic energy; exothermic reaction
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Why do chemical reactions tend to speed up when the concentration of the reactants is increased?
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The reactants collide more often.
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One carbon atom with four valence electrons combines with ____ hydrogens, each with one valence electron, to fill the outer orbital with _______electrons
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4:8
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What aspects of amino acid structure vary among different amino acids?
answer
The components of the R-group
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Which one of the following is not a component of each amino acid used to make proteins?
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a phosphorous atom, P
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Polymers of amino acids are formed via _____________ reactions that form ___________ bonds.
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condensation; peptide
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Which of the following observations is the strongest argument in favor of the hypothesis that protein structure and function are correlated?
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Denatured (unfolded) proteins do not function normally.
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An enzyme has a total of four active sites. When you denature the molecule and study its composition, you find that each active site occurs on a different polypeptide. Which of the following hypotheses does this observation support?
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The protein has quaternary structure.
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The lock-and-key analogy for enzymes applies to the _____.
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specificity of enzymes binding to their substrate
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Several of the molecules called vitamins act as enzyme cofactors. Vitamin deficiencies cause disease. What is the most direct explanation for this?
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If cofactors are missing, enzymes cannot function properly, and important reaction products will be absent from cells.
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The rate of an enzyme-catalyzed reaction depends on four factors. Which of these is not one of these?
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Amount of energy available
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When nucleotides polymerize to form a nucleic acid _____.
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a covalent bond forms between the sugar of one nucleotide and the phosphate of a second
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What is the difference between a ribonucleotide and a deoxyribonucleotide?
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Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.
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Which of the following includes all of the pyrimidines found in RNA and/or DNA?
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cytosine, uracil, and thymine
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A nucleotide is made up of which of the following subunits?
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a 5-carbon sugar, a phosphate group, and a nitrogenous base
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Nucleic acids have a definite polarity, or directionality. Stated another way, one end of the molecule is different from the other end. How are these ends described?
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One end has an unlinked 3 carbon; the other end has an unlinked 5 carbon.
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. What forms the "backbone" of a nucleic acid?
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a chain of sugar and phosphate groups, linked through phosphodiester bonds
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Why do researchers think the first self-replicating molecule was RNA?
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RNA has the capacity to provide a template and is known to catalyze reactions.
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In a DNA double helix, the chemical bonds that form between the complementary nitrogenous bases are _____.
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hydrogen bonds
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Which of the following can vary among monosaccharides?
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the number of carbon atoms
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Which of the following carbohydrates contains a peptide bond?
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peptidoglycan
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Carbohydrates perform a wide variety of functions in cell. Which of is not a function of carbohydrtaes?
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All of the above are functions of carbohydrates
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Which complex carbohydrate is a storage form of energy in animals?
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Glycogen
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Carbohydrates that function as structural molecules are extraordinarily resistant to degradation and decay. Which structural feature best explains why?
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Structural polysaccharides are built with ?beta-1,4-glycosidic linkages, which only a few enzymes can break.
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How do the ?and ? forms of glucose differ?
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Their ring structures differ in the location of a hydroxyl group.
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Which of the following types of molecules would have the highest capacity to store chemical energy?
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a six-carbon molecule rich in C-H bonds, such as a lipid
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If you were going to develop a new antibiotic, you would probably need to become an expert on which of these carbohydrates?
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peptidoglycan
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Phospholipid bilayer membranes are selectively permeable. What is meant by the phrase "selectively permeable"?
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allows some things to cross while restricting others
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Which aspect of phospholipids is most important to the formation of bilayers?
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They are amphipathic..
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Lipid bilayers are highly selective. What diffuses across this membrane with the most ease?
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small, uncharged polar molecules
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What membrane model is the most accepted by modern science concerning the cell membrane structure?
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Fluid-mosaic model
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What distinguishes facilitated diffusion from simple diffusion?
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Membrane proteins help move molecules across the membrane.
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Which of the following means of transport would most likely be used for moving a medium-sized molecule (like a monosaccharide or an amino acid) from a low concentration on the outside of a cell to a high concentration on the inside of a cell?
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active transport through a "pump" protein
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____________ fatty acids and ____________ hydrocarbon chains increase membrane permeability.
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unsaturated; short
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Steroids are ________.
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a class of lipid with four-ring structure.
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What will happen to a red blood cell (rbc) which has an internal ion concentration of about 0.9 percent, if it is placed into a beaker of pure water?
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The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the rbc.
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Where would you most likely find an integral protein?
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spanning the cell membrane, with parts of the protein visible from both the inside and outside of the cell
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Kangaroo rats live in the desert of the southwestern United States. They have many adaptations to minimize water loss. They obtain a small amount of water from seeds that they eat. However, the rest of the water they obtain is from cellular respiration.
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This could be true, as water is produced in cellular respiration.
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The approximate yield of ATP molecules from the full oxidation of a molecule of glucose is:
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32
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In which form are electrons transferred during typical redox reactions such as the oxidation of glucose?
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as hydrogen atoms
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Which is not a stage of cellular respiration?
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photosynthesis
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Which one of the following represents the reduced forms of the two major electron carriers?
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NADH and FADH2
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Cellular respiration is a series of _____ reactions.
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catabolic
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The electron transport chain is part of:
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oxidative phosphorylation.
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In the first three stages of cellular respiration, the chemical energy in glucose is transferred to:
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electron carriers and ATP
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A molecule that is ______ loses electrons, and a molecule that is ______ gains electrons.
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oxidized; reduced
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In eukaryotes, pyruvate oxidation takes place in the:
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mitochondrial matrix.
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Which of the following sequences correctly represents the flow of energy through living systems?
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light photosynthesis carbohydrate cellular respiration ATP heat
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In plants and algae, __________ is the source of the electrons needed for photosynthesis.
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H2O
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During photosynthesis in plants and algae, __________ is oxidized and __________ is reduced.
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H2O; CO2
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Where does the oxygen come from that is produced as a by-product of photosynthesis?
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from breakdown of water
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Beginning with the step catalyzed by rubisco, arrange the steps in the Calvin cycle in the proper sequence in which they occur.
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A. carboxylation, reduction, regeneration
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The most abundant protein on Earth is thought to be:
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rubisco
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The primary reason surplus carbohydrates in plants are stored as starch is because:
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if they were left as individual monosaccharides, water would enter the cell by osmosis.
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Which of the following correctly lists the path taken by electrons through the light dependent reactions of photosynthesis?
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water photosystem II cytochrome b6f photosystem I NADPH
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In photosynthesis, the electrons from _____________________ are used to reduce ___________________.
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water; carbon dioxide
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ATP production in photosynthesis requires:
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light, electrons, and protons.
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What occurs when the signal causes release of dopamine in the brain, which causes relaxation and feelings of well-being?
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response
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A protein on a cell surface that binds to a signaling molecule is an example of which of the following elements of cellular communication?
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a receptor protein
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To have communication between cells, you must have a:
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All of these choices are correct.
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The opening of an ion channel as a result of nicotine binding is an example of:
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receptor activation
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In communication between cells, the _____________________ produces the signaling molecule, also known as the ________________; the ______________________ produces the _______________, to which the signaling molecule binds. A. ligand B. signaling cell C. receptor D. responding cell
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B, A, D, C
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A cell that responds to an environmental condition by the release of a chemical is an example of which of the following elements of cellular communication?
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a signaling cell
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Signal transduction results in:
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a response by the cell
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Of the choices below, what is the most likely reason that paracrine signaling does not activate the cell that is producing the signaling molecule?
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The cell does not have the proper receptor.
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Platelet-derived growth factor (PDGF) is a signaling molecule that functions in which of the following types of cell signaling?
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paracrine
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Which of the following statements about mammalian skin is incorrect?
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A specialized form of extracellular matrix, called the basal lamina, underlies the dermis and separates it from tissues below.
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Which is the correct order from lesser to greater complexity for the following?
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cells, tissues, organs
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Which of the following structures are responsible for the shape of a cell?
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cytoskeloton
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The basal lamina is:
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a specialized form of the extracellular matrix found beneath all epithelial tissues.
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A pathologist is carrying out an autopsy. Upon opening the chest cavity, the pathologist sees a thick, fibrous tissue surrounding the heart. This is likely:
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connective tissue
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Which of the following structures would be located in the dermis of the skin?
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all of the choices are correct
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The cytoskeleton of animal cells includes:
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microtubules, microfilaments, and intermediate filaments.
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Myosin motor proteins use ATP to:
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carry vesicles along a microfilament within a cell in a minus-to-plus direction.
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Cilia and flagella:
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are specialized organelles that propel some algae, plant, and animal cells.
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Dynamic instability is a:
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feature of microtubules.
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The correct sequence of steps in the eukaryotic cell cycle is:
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G1 S phase G2 mitosis cytokinesis.
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42. Prokaryotic cells and eukaryotic cells reproduce by mitotic cell division. Regardless of the type of cell, all cells must __________________ before they divide.
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make a copy of their genetic information
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Which of the following is not true about the eukaryotic cell cycle?
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Interphase is typically the shortest of the two stages of the cell cycle.
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A skin cell in G2 of interphase has _______________ as much DNA as it had in G1.
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twice
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All of the following happen during mitosis except:
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synthesis of DNA
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Paramecium is a single-cell eukaryotic organism that can reproduce by mitotic cell division. Prior to the M phase of the cell cycle, which of the following must occur?
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The cell must replicate its chromosomes.
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The division of the cell's cytoplasm in a eukaryotic cell is known as:
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cytokineses
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The correct sequence of steps in the M phase of the cell cycle is:
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prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis.
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49. Sister chromatids are best described as two DNA molecules that have:
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virtually identical sequences of nucleotides
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What is the function of histone proteins?
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to package DNA in eukaryotic chromosomes
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What is a major difference in the extracellular matrix (ECM) between plant and animal cells?
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Plant ECM is primarily carbohydrate in nature, whereas animal ECM is largely protein based.
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The production of alcohol or lactate from pyruvate during __________ occurs as a means of regenerating __________ from __________.
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fermentation; NAD+; NADH
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Why are there several structurally different pigments in the reaction centers of photosystems?
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This setup enables the plant to absorb energy from sunlight from a variety of wavelengths.
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Which of the following statements is NOT true of mitosis?
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Homologous chromosomes synapse in prophase.
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A human cell has 46 total or 23 pairs of chromosomes. Following mitosis, the daughter cells would each have a total of ______ chromosomes. After meiosis I, the two daughter cells would have _____chromosomes, and after meiosis II ______ chromosomes.
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. 46, 23, 23
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The correct sequence of steps in the eukaryotic cell cycle is:
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G1 S phase G2 mitosis cytokinesis.
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Which of the following is not true about the eukaryotic cell cycle?
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Interphase is typically the shortest of the two stages of the cell cycle.
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A skin cell in G2 of interphase has _______________ as much DNA as it had in G1.
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twice
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A gene associated with promoting normal cell division is called:
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a proto-oncogene.
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An enzyme that catalyzes the addition of a phosphate group from ATP to another molecule is called a:
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kinase
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In observing DNA replication in the lab, you notice that in some cells, a defect occurs where DNA replication proceeds, but the RNA primers are not removed and replaced with DNA. Which enzyme is most likely to be defective in this system?
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DNA polymerase
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The fact that DNA replication occurs in virtually the same way in all organisms reflects:
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its origin early in the history of life.
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_________ relieves the tension on the double helix during DNA replication.
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Topoisomerase
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Which of the following statements about the strands of a newly replicated DNA molecule is correct?
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One strand is new and the other is from the original molecule.
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Energy is required in order to add a nucleotide to the growing strand of DNA during replication. From where does that energy come?
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an incoming nucleotide
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RNA is involved in which of the following cellular processes?
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DNA replication, transcription, and translation
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Telomerase is fully active in _____ and _____ cells, but almost completely inactive in ____ cells.
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germ; stem; somatic
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Which of the following statements is true regarding chromosome replication in eukaryotes?
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During chromosome replication, multiple origins of replication form for all DNA in a cell.
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A shotgun sequencing project yields the following sequence for a strand of DNA. 5'-GGTTTGGAGTAT-3'
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5?-GAGTATCCAAAT-3?
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Genome sequencing includes the following steps: 1. putting the sequences in the correct order 2. matching regions of overlap 3. breaking the DNA into small fragments 4. reconstructing the long sequence of nucleotides 5. sequencing the DNA In what order are these steps carried out?
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3-5-2-1-4
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Sometimes a single-stranded molecule of RNA is able to fold back on itself because the nucleotide sequence on one part of the RNA is complementary to another part. This sequence motif results in a:
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hairpin-shaped structure.
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All of the genetic material transferred from a parent to an offspring is known as a:
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genome
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Which of the following would be found in DNA sequences but not in mRNA sequences?
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transcription start sites
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The genome of a virus can contain which of the following?
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all of these choices are correct
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The size of a genome is measured by:
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the number of base pairs.
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Transposable elements are:
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DNA sequences that can insert themselves into new positions within the genome.
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Why do mutations associated with cancer almost always occur sequentially instead of simultaneously?
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all of these choices are correct
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A family can share a genetic risk of developing cancer if:
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C. a germ-line mutation in one of the genes implicated in the cancer occurred in an ancestor
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Sites in the genome that are more susceptible to mutations than others are called:
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hotspots
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Which of the following would you expect to have the lowest rate of point mutations per replication?
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human
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Which of the following statements applies to frameshift mutations?
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They change the amino acid sequence downstream from the mutant site.
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Which of the following is most likely to result in a nonfunctional polypeptide?
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a nonsense mutation
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Which of the following statements about mutations is true? A mutation:
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may leave the amino acid sequence of a protein unchanged.
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A point mutation that changes a UAC codon into a UAG codon is a:
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a nonsense mutation
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The phenotype of an individual results from an interaction between:
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genotype and the environment.
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Which of the following statements best describes the effect of having the S allele, which codes for sickle-cell anemia?
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The effect depends on whether the allele occurs in its homozygous or heterozygous form, and the environment (i.e., whether malaria is present).
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An individual is homozygous for a gene if
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they developed from a sperm and an egg that carried the same allele.
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Which statements about mutations are false?
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Mutations are usually caused by exposure to radiation.
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"Any difference among individuals that is sufficiently common such that it would almost certainly be present in a group of 50 individuals chosen at random" is the definition of a(n):
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polymorphism.
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Which one of the following best describes genotype-by-environment interactions?
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Genetic and environmental factors combine to influence phenotype.
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Which one of the following statements about restriction fragment length polymorphisms (RFLPs) is correct?
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all of these choices are correct
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In England, a man who is upset about the amount of dog feces on his lawn supposedly collected hair samples from neighborhood dogs and compared their DNA types with that of the feces, thereby identifying the offending dog (and the negligent owner). It this possible?
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This is not only possible, but it is fairly easy.
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______ suggests that traits in offspring resemble the average of the parents.
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blending inheritance
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In a reciprocal cross:
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the sexes are interchanged relative to the trait.
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In Mendel's garden peas, each cell in a pea plant has a total of:
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two alleles for each gene
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An allele is
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one of the several forms of a gene
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In genetic crosses, the symbol Aa refers to a:
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genotype
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Which of the following was not a trait that Mendel studied in pea plants?
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leaf size
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Which of the following statements is true regarding Mendel's work?
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He focused on a subset of easily discernible traits in pea plants.
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Which of the following ratios is associated with Mendel's discoveries?
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all of these choices are correct
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A wild-type fruit fly:
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exhibits the most common phenotype in the population.
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. In fruit flies, an X chromosome carrying the allele for white eyes is transferred from a male to a female of the next generation and in the next generation is transmitted back to the male again. This is called:
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crisscross inheritance
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Which is longer the X chromosome or the Y?
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The X chromosome
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How many genes does the X chromosome have?
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1000 genes
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How many genes does the Y chromosome have?
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50 genes
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In many animal species there is a special pair of unmatched chromosomes called the
answer
sex chromosomes
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In humans, the sex chromosomes are called
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X and Y
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In human males, segregation of the X chromosome from the Y chromosome during anaphase I of meiosis results in
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half the sperm bearing an X chromosome and the other half bearing a Y chromosome.
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With random fertilization, half of the fertilized eggs are expected to be
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chromosomally XX and the other half XY, which is characteristic of Mendelian segregation.
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In the United States the sex ratio is approximately
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100 females : 105 males
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In 1910, Thomas Hunt Morgan found that, in the fruit fly, genes were present on
answer
chromosomes and that the X chromosome carried its own genes
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Genes in the X-chromosome are called
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X linked genes
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In Thomas Hunt's experiment, he found
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A mutant male fruit fly with white eyes
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The F1 generation produced
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all red-eyed offspring (recessive gene)
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When the F1 generation was crossed
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he found that the white-eyed flies returned to the population
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What was not expected was that the
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white-eyed offspring were male and that, of the males in the F2 generation, half had red eyes and the other half had white eyes. The ratio was 1:1
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X-linked recessive alleles are expressed in males because males have only one X-chromosome.
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males have only one X chromosome
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Once you know the patterns revealed, genotypes can be assigned to the
answer
original files
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In 1916, one of Morgan's graduate students, Calvin Bridges, was crossing the white-eyed female flies with red-eyed males and noticed that about 1 offspring in 2000 from the cross was
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"exceptional"—either a female with white eyes or a male with red eyes
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Bridges proposed that the X chromosomes in females occasionally fail to separate in anaphase I of meiosis and both the X chromosomes go to the same spindle pole.This resulted in
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two X's or no X's
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Females from Calvin Bridge's expiriement
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had eggs with XXY or males with XO (males without Y)
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This discovery also proved that, in the fruit fly
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male fertility but not male development was influenced by the absence of the Y chromosome.
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An example of an X-linked recessive mutation in humans is
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red green color blindness
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Features of X-linked inheritance include
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-Affected individuals are almost always males because males need only one copy of the mutant gene to be affected, whereas females need two copies. -Affected males have unaffected sons because males transmit their X chromosome only to their daughters. -A female whose father is affected can have affected sons because such a female must be a heterozygous carrier of the recessive mutant allele.
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One of the most famous examples of human X-linked inheritance is the trait of
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hemophilia
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When genes are close together on the same chromosome (autosome or sex chromosome),
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They are linked
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Sturtevant crossed mutant males (mutant for eye color and cross vein absence) with What was the result?
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wild type females -The result was an F1 generation that phenotypically had the wild-type characteristics.
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When the F1 offspring were crossed to each other (brother/sister matings
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the F2 progeny revealed interesting observations.
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Each male progeny receives its X chromosome from the ______ and its Y chromosome from the ______
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mother, father
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The phenotype of each male immediately reveals the genetic constitution of the
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X chromosome that the male inherited from the mother.
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Crossing over in prophase I of meiosis is a physical exchange of chromosome parts.
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physical exchange of chromosome parts
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Crossing over results in
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two recombinant and two nonrecombinant chromosomes
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Nonrecombinant alleles can also appear when
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crossing over does not take place between the two genes.
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The frequency of recombination is a measure of
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is a measure of the distance between linked genes.
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For two genes found on the same chromosome, they may be located very far from each other and crossing over is
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likely to occur
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genes may be found very close together
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making a crossover event less likely.
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The frequency of recombination between any two genes ranges
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depends on the distance between the gene
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The frequency of recombination can be used
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as a measure of the physical distance between genes
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Genetic maps are built up step by step as
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new genes are discovered that are genetically linked with known genes.
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Across short distances on a genetic map, the map units are additive and their expected frequency can
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can be determined by adding the distance between them.
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Genetic risk factors for disease can be localized by
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genetic mapping
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single-nucleotide polymorphism(SNP)
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are the most common type of genetic variation among people.
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The SRY gene
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is responsible for the initiation of male sex determination in humans.
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Y-linked genes
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are those that are present in a unique region of the Y chromosome, where they cannot cross over with the X chromosome.
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Y linked genes are
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These genes are transmitted from father to son to grandson.
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No physical traits are known that follow a strict Y-linked patterns of inheritance.This emphasizes the extremely low density of functional genes in the Y chromosome.
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True
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A haleotype is
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a combination of alleles at adjacent locations on a chromosome that are inherited together
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The mutations creating new Y-chromosome haplotypes were occurring at the same time as
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populations were migrating and founding new settlements across the globe ( This led to each geographically distinct population came to have a somewhat different set of Y-chromosome haplotypes.)
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Neighboring populations tend to have more closely related Y chromosome than more
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distant populations
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The clustering of the Y-chromosome haplotypes correspond with the
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spread of human settlements around the globe inferred from archaeological evidence.
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Name the different types of inheritance of cytoplasmic organelles
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maternal, paternal, and biparental
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Maternal inheritance
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the organelles in the offspring cells derive from those in the mother
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Paternal inheritance
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the organelles in the offspring cells derive from those in the father
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Biparental
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the organelles in the offspring cells derive from those in both parents
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In most organisms, either _______ or _______ inheritance predominates.
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maternal, parental
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Maternal inheritance is characteristic of
answer
mitochondrial diseases
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Pedigree for the MERRF syndrome
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Both males and females can show the trait, All offspring from an affected female show the trait, and Males never transmit the trait to their offspring.
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Because mitochondrial DNA does not undergo recombination and is maternally inherited
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it can be used to trace human ancestry and migration.
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The traits that Mendel studied were
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single gene traits
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Complex traits are influenced by
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multiples genes as well as by the enviroment
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Single gene traits are
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determined by variation and not influenced by the enviroment
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Which are more common, Complex traits or single gene traits?
answer
Complex traits
question
What are some examples of complex traits?
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height, number of eggs laid by hens, and milk production in cows
question
Name some common human diseases are also complex traits
answer
high blood pressure, obesity, diabetes and depression
question
In many complex traits, the phenotype is determined by a
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measurement (height in inches, milk by the gallon, number of eggs, etc) known as quantitative traits
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Quantitive traits
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are measured along a continuum with only small intervals between similar individuals.
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By contrast, single-gene traits often appear in one of two or a few different phenotypes
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Ex: round vs. wrinkled seeds
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Expression of complex traits is susceptible to
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lifestyle choices and other environmental factors
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true-breeding (homozygous) strains are also called
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inbred lines
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Complex traits are affected by multiple genes and as a result, the
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phenotype and genotype ratios observed by Mendel are not observed
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The number of genes affecting complex traits is usually so large that
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different genotypes can have very similar phenotypes, making it difficult to see the effects of individual genes on a trait.
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The phenotypes of many complex traits, including human height, conform to a
answer
normal distribution
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Genetic and environmental effects can interact in
answer
unpredictable ways
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This type of interaction is important because it implies that
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the effect of a genotype cannot be specified without knowing the environment, and the other way around.
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These results also imply that there may be
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no genotype that is the "best" across a broad range of environments, and likewise no environment is "best" for all genotypes.
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Genotype-by-environment interaction implies that the
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the interplay between genes and the environment is difficult to predict.
question
Here, the animals are adults of two inbred lines of mice. When fed a normal diet both lines grow to be about the same size. When fed a high-fat diet, however, the inbred line A becomes obese, whereas inbred line B does not. Line A is an example of:
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Therefore, it is not genotype alone that causes obesity in line A because, with a normal diet, line A does not become obese. Nor is it a high-fat diet alone that causes obesity because the high-fat diet does not cause obesity in line B. genotype by enviroment interaction
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Francis Galton (cousin of Charles Darwin) studied
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complex traits such as height, strength, and physical characteristics in humans
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He concluded from his studies that children of tall parents are
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taller than the average population but shorter than their parents on average.
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Children from shorter parents have offspring that are, on average
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taller than their parents but shorter than the average of the population.
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Galton's analysis led him to the trend called
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Regression toward the mean
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Regression toward the mean is
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the phenomenon that if a variable is extreme on its first measurement, it will tend to be closer to the average on its second measurement—and if it is extreme on its second measurement, it will tend to have been closer to the average on its first.
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The regression toward the mean is
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1. During meiosis, segregation and recombination break up combinations of genes that results in extreme phenotypes 2. parents results not only from genes, but also from the environment.
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Are environmental effect inherited
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no
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Heritability
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is the proportion of the total variation due to genetic differences among individuals.
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For a complex trait, the heritability determines how
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closely the mean of the progeny resembles that of the parents.
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When heritability is 100%, all of the variation among individuals in the population is due to
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Differing genotypes
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Galton also pioneered studies of twins as a way to separate the effects of genotype and environment in _______ differences among individuals.
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phenotypic
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Identical (maternal) twins arise from a single fertilized egg, which, after several rounds of cell division
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separate into two distinct but genetically identical embryos.
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Fraternal twins result when two separate eggs, produced by double ovulation, are fertilized by two different sperm, making them only
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as closely related as any other pair of siblings.
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Concordance is defined as the
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the percentage of cases in which both members of a pair of twins show the trait when it is known that at least one member shows it.
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High concordance rates suggest that all of these disorders have an
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important genetic component.
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The most common birth defects are affected by
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multiple genetic risk factors.
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Examples of Mendelian Disorders
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cystic fibrosis or sickle-cell anemia
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But the majority of birth anomalies are affected by
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both genetic and environmental risk factors.
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Some ______ have relatively large effects, while others have small ones.
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genes
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For the majority of genes that contribute to a complex trait, the magnitude of their individual effects is typically
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quite small
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The multiple genetic and environmental factors affecting complex traits imply that different people can have the same disease
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for different reasons
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Examples of diseases with different causes:
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breast cancer, emphysma, high cholesterol, high blood pressure and depression
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The traditional strategy for treating diseases is to use the same medicine for everyone with the same disease. However, since we now know that the same disease may have different causes
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personalized medicine has emerged.
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Personalized medicine
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matches the treatment to the patient and not to the disease.
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The human body contains about ______ major cell types
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200
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Most common chemical modification to DNA is the
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addition of a methyl group to the base cytosine. Mostly occurs in cytosine bases that are adjacent to guanosine bases on a DNA strand.
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What does "p" represent in the Cpg?
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phosphate between two nucleotides
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CpG sites are often clustered near the _____ of the gene. These clusters are referred to as _____.
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promoter, CpG islands
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Methylation of a CpG island can change over time or in response to environmental cues, providing a
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way to turn genes on and off
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Eukaryotic DNA is packaged as ________, a complex of DNA, RNA, and proteins that gives chromosomes their structure.
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chromatin
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When the chromatin is coiled, the proteins that carry out transcription
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cannot access the DNA
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The chromatin must unravel to allow space for transcriptional enzymes and proteins to work. This is accomplished by
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chromatin remodeling
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During chromosome remodeling, the nucleosomes are repositioned to expose different
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stretches of DNA
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Epigenchanges are not to the DNA sequence itself, but to the manner in which the DNA is packaged, sometimes causing
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changes in gene expression
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These changes can be inherited but are often reversible and responsive to
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changes in the enviroment
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This differential regulation is called
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dosage compensation
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Xist gene is normally transcribed at very
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low levels
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DNA methylation
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is an epigenetic mechanism used by cells to control gene expression.
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General transcription factors bind to the
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gene's promoter
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The transcription factors are brought there by one of the proteins that binds to a short sequence called the
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TATA box
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General transcription factors recruit the components of the
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RNA polymerase complex which synthesizes the
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Regulatory transcription factors bind at
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enhancer sequences and also to the general transcription factors at the promoter region
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The general transcription factors can then recruit the
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polymerase complex.
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RNA splicing provides an opportunity for
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regulating gene expression
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The same primary transcript can be spliced in different ways to yield different proteins, This is called
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alternative splicing
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Some RNA transcripts become substrates for enzymes that
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chemically modify bases in the RNA
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Chemically modifying bases in the RNA results in
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a change to the nucleotide sequence and the amino acid sequence (called RNA editing)
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RNA editing results in
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transcripts from the same gene can produce multiple types of proteins even in a single cell.
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Specific example of RNA editing:
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apolipoprotein B
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Small regulatory RNAs regulate gene expression by either
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binding to transcripts and blocking translation or binding to transcripts and causing degradation
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Two types of small regulatory RNAs are
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microRNAs and small interfering RNAs.
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MicroRNAs are
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Are transcribed just like protein-coding genes, using the same RNA polymerase and going through capping, splicing, and polyadenlyation.
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RISC (RNA-induced silencing complex)
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a multiprotein complex, specifically a ribonucleoprotein, which incorporates one strand of a single-stranded RNA
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Translation of mRNA into protein provides another level of control of
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gene expression
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postranslational modification
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after translation, proteins can be modified in multiple ways that regulate their structure and function
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In prokaryotes, gene regulation is simpler than in eukaryotes because
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DNA is not packaged into chromosomes mRNA is not processed there is not a nuclear membrane separating the processes of transcription and translation
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Positive regulation: a regulatory molecule (activator protein) binds DNA in order for
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transcription to take place
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operon
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region of DNA that includes the coding sequence for multiple genes, that get transcribed together into a single molecule of mRNA (polycistronic mRNA).
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The lacI gene (encoding the repressor protein) is expressed constantly at
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low level
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In the absence of lactose, the repressor binds with the
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operator
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In the presence of lactose
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-the repressor protein is unable to bind to the operator, -RNA polymerase is recruited, -transcription occurs.
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Lactose acts as an
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inducer
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It is _______ that binds the repressor and prevents it from binding the operator.
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allolactose
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Additional levels of regulation also exist with the
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lac operon
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The role of CRP-cAMP is to provide another level of control of transcription that is more sensitive to the nutritional needs of the cell than the level of control provided by the
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presence or absence of lactose.
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When a bacterial cell is infected with a bacteriophage, the phage genome is injected into the
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bacterial cell
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Development
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is the process in which a fertilized egg undergoes multiple rounds of cell division to become an embryo with specialized tissues and organs.
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Gene regulation allows cells to become specialized in the process of
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differentation
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A fertilized human egg is a cell because it can give rise to a complete organism and the membranes that support a developing embryo.
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totipotent
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A human egg is fertilized in the fallopian tubes, becoming a
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zygote
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These cells rearrange themselves, forming a hollow sphere called a
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blastocyst
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In one region of the blastocyst, there is a group of cells called the
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inner cell mass
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The cells of the inner cell mass are _______ stem cells and ______ because they can give rise to any of the three germ layers and therefore any cell of the body.
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embryonic, pluripotent
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Changes in gene expression: When cells become committed to a particular developmental pathway, genes no longer needed are
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turned off and difficult to turn on again
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Gene loss
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As cells become differentiated, they delete the DNA for genes they no longer need.
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nuclear transfer
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John Gurdon transferred nuclei from differentiated cells into unfertilized eggs whose nuclei had been inactivated with UV light
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_________ play a prominent role in regenerative medicine and are already used in bone marrow transplants.
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Stem cells
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Embryonic stem cells are ______
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pluripotent
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Gene regulation during development is
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hierarchical
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Bicoid
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mutants lack anterior segments
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Nanos
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mutants lack posterior segments.
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Drosophila oocytes are highly
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polarized
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The bulk of bicoid mRNA comes from the
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mother
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Three other classes of developmental genes expressed in hierarchy:
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gap genes, pair-rule genes, and segment polarity genes
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Homeotic genes encode __________
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transcription factors
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Molecules that are similar in sequence among distantly related organisms are said to be
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evolutionarily conserved
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Pax6 is a transcription factor, and when mutated, it is found to cause mutations
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fly, mouse, and human eye development.
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Signal transduction
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a extracellular molecule acts as a signal to activate a membrane protein that in turn activates molecules inside the cell that control differentiation.
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The signaling molecule is the
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ligand
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The membrane protein that it activates is the
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receptor
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In spite of a high degree of phenotypic variation, humans actually rank ______ in terms of overall genetic variation.
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low
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A species is a group of individuals that can exchange genetic material through interbreeding
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or share alleles through reproduction.
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The alleles that are shared are from a single gene pool for that species. In other words, the gene pool consists of all
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the alleles present in all individuals in a species
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A population is an
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interbreeding group of organisms of the same species living in the same geographical area.
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Genetic variation can occur through
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mutation and recombination
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Mutations can be _______ (in the body's tissues) or ________ (in the reproductive cells that are passed to the next generation).
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somatic, germ line
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The frequency of an allele is simply the number of that particular allele present in a population
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divided by the total number of alleles.
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Natural selection
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is the change in an allele's frequency over time based on that particular allele's impact on survival and reproduction.
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Stabilizing selection
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selects against the extremes. Example: human birth weight.
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Directional selection
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selects against one of the two extremes. Example: drug resistance in viruses, bacteria, and parasites.
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Disruptive selection
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selects against the mean. Example: birds' bills
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The enzyme _____ compensates for chromosomes shortening at the tips after each round of DNA replication.
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telomerase
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The C-value paradox applies to:
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eukaryotes
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Chromosomal mutations that are most likely to cause serious damage to an organism are those that affect the:
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centromere
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You are working in a medical research lab and have to determine if a patient is heterozygous or homozygous for a particular restriction site. You isolate a region of DNA from each chromosome, the middle of which could contain the restriction site, if the patient has it. If you treat the DNA with the restriction enzyme, how many fragments will be produced if the patient is heterozygous for the presence of the restriction site?
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Three
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