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.

question

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?

answer

Lance Armstrong, because he has reproduced

question

Carl Woese et al. studied small __________molecules and established the concept of the ____________.

answer

rRNA; domains

question

In the diagram below, "A" is _____ ; "B" is _____.

answer

the results of several experiments support the hypothesis.

question

Which of the following statements is true about biological studies?

answer

Hypotheses may be tested by a combination of observation, measurement, and experimentation.

question

Water has what type bonds?

answer

polar covalent

question

How many electrons are involved in a double covalent bond?

answer

four

question

An atom has six electrons in its valence shell. How many single covalent bonds would you expect it to form in most circumstances?

answer

two

question

If an atom is electrically neutral, which of the following must be true?

answer

It has the same number of protons as electrons.

question

. Which of the following is a violation of the first law of thermodynamics?

answer

The universe will eventually die, and it will have no energy left in it.

question

Water also has several remarkable properties, largely due to its ability to form hydrogen bonds. Which property does NOT apply to water?

answer

All of the above are properties of water

question

A pH of _____is considered neutral and a pH of ______ is acidic.

answer

7;3

question

The energy of movement is called __________ and produces an_______________ reaction.

answer

kinetic energy; exothermic reaction

question

Why do chemical reactions tend to speed up when the concentration of the reactants is increased?

answer

The reactants collide more often.

question

One carbon atom with four valence electrons combines with ____ hydrogens, each with one valence electron, to fill the outer orbital with _______electrons

answer

4:8

question

What aspects of amino acid structure vary among different amino acids?

answer

The components of the R-group

question

Which one of the following is not a component of each amino acid used to make proteins?

answer

a phosphorous atom, P

question

Polymers of amino acids are formed via _____________ reactions that form ___________ bonds.

answer

condensation; peptide

question

Which of the following observations is the strongest argument in favor of the hypothesis that protein structure and function are correlated?

answer

Denatured (unfolded) proteins do not function normally.

question

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?

answer

The protein has quaternary structure.

question

The lock-and-key analogy for enzymes applies to the _____.

answer

specificity of enzymes binding to their substrate

question

Several of the molecules called vitamins act as enzyme cofactors. Vitamin deficiencies cause disease. What is the most direct explanation for this?

answer

If cofactors are missing, enzymes cannot function properly, and important reaction products will be absent from cells.

question

The rate of an enzyme-catalyzed reaction depends on four factors. Which of these is not one of these?

answer

Amount of energy available

question

When nucleotides polymerize to form a nucleic acid _____.

answer

a covalent bond forms between the sugar of one nucleotide and the phosphate of a second

question

What is the difference between a ribonucleotide and a deoxyribonucleotide?

answer

Ribonucleotides have a hydroxyl group on the 2 carbon of their sugar subunit.

question

Which of the following includes all of the pyrimidines found in RNA and/or DNA?

answer

cytosine, uracil, and thymine

question

A nucleotide is made up of which of the following subunits?

answer

a 5-carbon sugar, a phosphate group, and a nitrogenous base

question

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?

answer

One end has an unlinked 3 carbon; the other end has an unlinked 5 carbon.

question

. What forms the "backbone" of a nucleic acid?

answer

a chain of sugar and phosphate groups, linked through phosphodiester bonds

question

Why do researchers think the first self-replicating molecule was RNA?

answer

RNA has the capacity to provide a template and is known to catalyze reactions.

question

In a DNA double helix, the chemical bonds that form between the complementary nitrogenous bases are _____.

answer

hydrogen bonds

question

Which of the following can vary among monosaccharides?

answer

the number of carbon atoms

question

Which of the following carbohydrates contains a peptide bond?

answer

peptidoglycan

question

Carbohydrates perform a wide variety of functions in cell. Which of is not a function of carbohydrtaes?

answer

All of the above are functions of carbohydrates

question

Which complex carbohydrate is a storage form of energy in animals?

answer

Glycogen

question

Carbohydrates that function as structural molecules are extraordinarily resistant to degradation and decay. Which structural feature best explains why?

answer

Structural polysaccharides are built with ?beta-1,4-glycosidic linkages, which only a few enzymes can break.

question

How do the ?and ? forms of glucose differ?

answer

Their ring structures differ in the location of a hydroxyl group.

question

Which of the following types of molecules would have the highest capacity to store chemical energy?

answer

a six-carbon molecule rich in C-H bonds, such as a lipid

question

If you were going to develop a new antibiotic, you would probably need to become an expert on which of these carbohydrates?

answer

peptidoglycan

question

Phospholipid bilayer membranes are selectively permeable. What is meant by the phrase "selectively permeable"?

answer

allows some things to cross while restricting others

question

Which aspect of phospholipids is most important to the formation of bilayers?

answer

They are amphipathic..

question

Lipid bilayers are highly selective. What diffuses across this membrane with the most ease?

answer

small, uncharged polar molecules

question

What membrane model is the most accepted by modern science concerning the cell membrane structure?

answer

Fluid-mosaic model

question

What distinguishes facilitated diffusion from simple diffusion?

answer

Membrane proteins help move molecules across the membrane.

question

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?

answer

active transport through a "pump" protein

question

____________ fatty acids and ____________ hydrocarbon chains increase membrane permeability.

answer

unsaturated; short

question

Steroids are ________.

answer

a class of lipid with four-ring structure.

question

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?

answer

The cell would swell because the water in the beaker is hypotonic relative to the cytoplasm of the rbc.

question

Where would you most likely find an integral protein?

answer

spanning the cell membrane, with parts of the protein visible from both the inside and outside of the cell

question

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.

answer

This could be true, as water is produced in cellular respiration.

question

The approximate yield of ATP molecules from the full oxidation of a molecule of glucose is:

answer

32

question

In which form are electrons transferred during typical redox reactions such as the oxidation of glucose?

answer

as hydrogen atoms

question

Which is not a stage of cellular respiration?

answer

photosynthesis

question

Which one of the following represents the reduced forms of the two major electron carriers?

answer

NADH and FADH2

question

Cellular respiration is a series of _____ reactions.

answer

catabolic

question

The electron transport chain is part of:

answer

oxidative phosphorylation.

question

In the first three stages of cellular respiration, the chemical energy in glucose is transferred to:

answer

electron carriers and ATP

question

A molecule that is ______ loses electrons, and a molecule that is ______ gains electrons.

answer

oxidized; reduced

question

In eukaryotes, pyruvate oxidation takes place in the:

answer

mitochondrial matrix.

question

Which of the following sequences correctly represents the flow of energy through living systems?

answer

light photosynthesis carbohydrate cellular respiration ATP heat

question

In plants and algae, __________ is the source of the electrons needed for photosynthesis.

answer

H2O

question

During photosynthesis in plants and algae, __________ is oxidized and __________ is reduced.

answer

H2O; CO2

question

Where does the oxygen come from that is produced as a by-product of photosynthesis?

answer

from breakdown of water

question

Beginning with the step catalyzed by rubisco, arrange the steps in the Calvin cycle in the proper sequence in which they occur.

answer

A. carboxylation, reduction, regeneration

question

The most abundant protein on Earth is thought to be:

answer

rubisco

question

The primary reason surplus carbohydrates in plants are stored as starch is because:

answer

if they were left as individual monosaccharides, water would enter the cell by osmosis.

question

Which of the following correctly lists the path taken by electrons through the light dependent reactions of photosynthesis?

answer

water photosystem II cytochrome b6f photosystem I NADPH

question

In photosynthesis, the electrons from _____________________ are used to reduce ___________________.

answer

water; carbon dioxide

question

ATP production in photosynthesis requires:

answer

light, electrons, and protons.

question

What occurs when the signal causes release of dopamine in the brain, which causes relaxation and feelings of well-being?

answer

response

question

A protein on a cell surface that binds to a signaling molecule is an example of which of the following elements of cellular communication?

answer

a receptor protein

question

To have communication between cells, you must have a:

answer

All of these choices are correct.

question

The opening of an ion channel as a result of nicotine binding is an example of:

answer

receptor activation

question

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

answer

B, A, D, C

question

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?

answer

a signaling cell

question

Signal transduction results in:

answer

a response by the cell

question

Of the choices below, what is the most likely reason that paracrine signaling does not activate the cell that is producing the signaling molecule?

answer

The cell does not have the proper receptor.

question

Platelet-derived growth factor (PDGF) is a signaling molecule that functions in which of the following types of cell signaling?

answer

paracrine

question

Which of the following statements about mammalian skin is incorrect?

answer

A specialized form of extracellular matrix, called the basal lamina, underlies the dermis and separates it from tissues below.

question

Which is the correct order from lesser to greater complexity for the following?

answer

cells, tissues, organs

question

Which of the following structures are responsible for the shape of a cell?

answer

cytoskeloton

question

The basal lamina is:

answer

a specialized form of the extracellular matrix found beneath all epithelial tissues.

question

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:

answer

connective tissue

question

Which of the following structures would be located in the dermis of the skin?

answer

all of the choices are correct

question

The cytoskeleton of animal cells includes:

answer

microtubules, microfilaments, and intermediate filaments.

question

Myosin motor proteins use ATP to:

answer

carry vesicles along a microfilament within a cell in a minus-to-plus direction.

question

Cilia and flagella:

answer

are specialized organelles that propel some algae, plant, and animal cells.

question

Dynamic instability is a:

answer

feature of microtubules.

question

The correct sequence of steps in the eukaryotic cell cycle is:

answer

G1 S phase G2 mitosis cytokinesis.

question

42. Prokaryotic cells and eukaryotic cells reproduce by mitotic cell division. Regardless of the type of cell, all cells must __________________ before they divide.

answer

make a copy of their genetic information

question

Which of the following is not true about the eukaryotic cell cycle?

answer

Interphase is typically the shortest of the two stages of the cell cycle.

question

A skin cell in G2 of interphase has _______________ as much DNA as it had in G1.

answer

twice

question

All of the following happen during mitosis except:

answer

synthesis of DNA

question

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?

answer

The cell must replicate its chromosomes.

question

The division of the cell's cytoplasm in a eukaryotic cell is known as:

answer

cytokineses

question

The correct sequence of steps in the M phase of the cell cycle is:

answer

prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis.

question

49. Sister chromatids are best described as two DNA molecules that have:

answer

virtually identical sequences of nucleotides

question

What is the function of histone proteins?

answer

to package DNA in eukaryotic chromosomes

question

What is a major difference in the extracellular matrix (ECM) between plant and animal cells?

answer

Plant ECM is primarily carbohydrate in nature, whereas animal ECM is largely protein based.

question

The production of alcohol or lactate from pyruvate during __________ occurs as a means of regenerating __________ from __________.

answer

fermentation; NAD+; NADH

question

Why are there several structurally different pigments in the reaction centers of photosystems?

answer

This setup enables the plant to absorb energy from sunlight from a variety of wavelengths.

question

Which of the following statements is NOT true of mitosis?

answer

Homologous chromosomes synapse in prophase.

question

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.

answer

. 46, 23, 23

question

The correct sequence of steps in the eukaryotic cell cycle is:

answer

G1 S phase G2 mitosis cytokinesis.

question

Which of the following is not true about the eukaryotic cell cycle?

answer

Interphase is typically the shortest of the two stages of the cell cycle.

question

A skin cell in G2 of interphase has _______________ as much DNA as it had in G1.

answer

twice

question

A gene associated with promoting normal cell division is called:

answer

a proto-oncogene.

question

An enzyme that catalyzes the addition of a phosphate group from ATP to another molecule is called a:

answer

kinase

question

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?

answer

DNA polymerase

question

The fact that DNA replication occurs in virtually the same way in all organisms reflects:

answer

its origin early in the history of life.

question

_________ relieves the tension on the double helix during DNA replication.

answer

Topoisomerase

question

Which of the following statements about the strands of a newly replicated DNA molecule is correct?

answer

One strand is new and the other is from the original molecule.

question

Energy is required in order to add a nucleotide to the growing strand of DNA during replication. From where does that energy come?

answer

an incoming nucleotide

question

RNA is involved in which of the following cellular processes?

answer

DNA replication, transcription, and translation

question

Telomerase is fully active in _____ and _____ cells, but almost completely inactive in ____ cells.

answer

germ; stem; somatic

question

Which of the following statements is true regarding chromosome replication in eukaryotes?

answer

During chromosome replication, multiple origins of replication form for all DNA in a cell.

question

A shotgun sequencing project yields the following sequence for a strand of DNA. 5'-GGTTTGGAGTAT-3'

answer

5?-GAGTATCCAAAT-3?

question

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?

answer

3-5-2-1-4

question

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:

answer

hairpin-shaped structure.

question

All of the genetic material transferred from a parent to an offspring is known as a:

answer

genome

question

Which of the following would be found in DNA sequences but not in mRNA sequences?

answer

transcription start sites

question

The genome of a virus can contain which of the following?

answer

all of these choices are correct

question

The size of a genome is measured by:

answer

the number of base pairs.

question

Transposable elements are:

answer

DNA sequences that can insert themselves into new positions within the genome.

question

Why do mutations associated with cancer almost always occur sequentially instead of simultaneously?

answer

all of these choices are correct

question

A family can share a genetic risk of developing cancer if:

answer

C. a germ-line mutation in one of the genes implicated in the cancer occurred in an ancestor

question

Sites in the genome that are more susceptible to mutations than others are called:

answer

hotspots

question

Which of the following would you expect to have the lowest rate of point mutations per replication?

answer

human

question

Which of the following statements applies to frameshift mutations?

answer

They change the amino acid sequence downstream from the mutant site.

question

Which of the following is most likely to result in a nonfunctional polypeptide?

answer

a nonsense mutation

question

Which of the following statements about mutations is true? A mutation:

answer

may leave the amino acid sequence of a protein unchanged.

question

A point mutation that changes a UAC codon into a UAG codon is a:

answer

a nonsense mutation

question

The phenotype of an individual results from an interaction between:

answer

genotype and the environment.

question

Which of the following statements best describes the effect of having the S allele, which codes for sickle-cell anemia?

answer

The effect depends on whether the allele occurs in its homozygous or heterozygous form, and the environment (i.e., whether malaria is present).

question

An individual is homozygous for a gene if

answer

they developed from a sperm and an egg that carried the same allele.

question

Which statements about mutations are false?

answer

Mutations are usually caused by exposure to radiation.

question

"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):

answer

polymorphism.

question

Which one of the following best describes genotype-by-environment interactions?

answer

Genetic and environmental factors combine to influence phenotype.

question

Which one of the following statements about restriction fragment length polymorphisms (RFLPs) is correct?

answer

all of these choices are correct

question

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?

answer

This is not only possible, but it is fairly easy.

question

______ suggests that traits in offspring resemble the average of the parents.

answer

blending inheritance

question

In a reciprocal cross:

answer

the sexes are interchanged relative to the trait.

question

In Mendel's garden peas, each cell in a pea plant has a total of:

answer

two alleles for each gene

question

An allele is

answer

one of the several forms of a gene

question

In genetic crosses, the symbol Aa refers to a:

answer

genotype

question

Which of the following was not a trait that Mendel studied in pea plants?

answer

leaf size

question

Which of the following statements is true regarding Mendel's work?

answer

He focused on a subset of easily discernible traits in pea plants.

question

Which of the following ratios is associated with Mendel's discoveries?

answer

all of these choices are correct

question

A wild-type fruit fly:

answer

exhibits the most common phenotype in the population.

question

. 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:

answer

crisscross inheritance

question

Which is longer the X chromosome or the Y?

answer

The X chromosome

question

How many genes does the X chromosome have?

answer

1000 genes

question

How many genes does the Y chromosome have?

answer

50 genes

question

In many animal species there is a special pair of unmatched chromosomes called the

answer

sex chromosomes

question

In humans, the sex chromosomes are called

answer

X and Y

question

In human males, segregation of the X chromosome from the Y chromosome during anaphase I of meiosis results in

answer

half the sperm bearing an X chromosome and the other half bearing a Y chromosome.

question

With random fertilization, half of the fertilized eggs are expected to be

answer

chromosomally XX and the other half XY, which is characteristic of Mendelian segregation.

question

In the United States the sex ratio is approximately

answer

100 females : 105 males

question

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

question

Genes in the X-chromosome are called

answer

X linked genes

question

In Thomas Hunt's experiment, he found

answer

A mutant male fruit fly with white eyes

question

The F1 generation produced

answer

all red-eyed offspring (recessive gene)

question

When the F1 generation was crossed

answer

he found that the white-eyed flies returned to the population

question

What was not expected was that the

answer

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

question

X-linked recessive alleles are expressed in males because males have only one X-chromosome.

answer

males have only one X chromosome

question

Once you know the patterns revealed, genotypes can be assigned to the

answer

original files

question

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

answer

"exceptional"—either a female with white eyes or a male with red eyes

question

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

answer

two X's or no X's

question

Females from Calvin Bridge's expiriement

answer

had eggs with XXY or males with XO (males without Y)

question

This discovery also proved that, in the fruit fly

answer

male fertility but not male development was influenced by the absence of the Y chromosome.

question

An example of an X-linked recessive mutation in humans is

answer

red green color blindness

question

Features of X-linked inheritance include

answer

-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.

question

One of the most famous examples of human X-linked inheritance is the trait of

answer

hemophilia

question

When genes are close together on the same chromosome (autosome or sex chromosome),

answer

They are linked

question

Sturtevant crossed mutant males (mutant for eye color and cross vein absence) with What was the result?

answer

wild type females -The result was an F1 generation that phenotypically had the wild-type characteristics.

question

When the F1 offspring were crossed to each other (brother/sister matings

answer

the F2 progeny revealed interesting observations.

question

Each male progeny receives its X chromosome from the ______ and its Y chromosome from the ______

answer

mother, father

question

The phenotype of each male immediately reveals the genetic constitution of the

answer

X chromosome that the male inherited from the mother.

question

Crossing over in prophase I of meiosis is a physical exchange of chromosome parts.

answer

physical exchange of chromosome parts

question

Crossing over results in

answer

two recombinant and two nonrecombinant chromosomes

question

Nonrecombinant alleles can also appear when

answer

crossing over does not take place between the two genes.

question

The frequency of recombination is a measure of

answer

is a measure of the distance between linked genes.

question

For two genes found on the same chromosome, they may be located very far from each other and crossing over is

answer

likely to occur

question

genes may be found very close together

answer

making a crossover event less likely.

question

The frequency of recombination between any two genes ranges

answer

depends on the distance between the gene

question

The frequency of recombination can be used

answer

as a measure of the physical distance between genes

question

Genetic maps are built up step by step as

answer

new genes are discovered that are genetically linked with known genes.

question

Across short distances on a genetic map, the map units are additive and their expected frequency can

answer

can be determined by adding the distance between them.

question

Genetic risk factors for disease can be localized by

answer

genetic mapping

question

single-nucleotide polymorphism(SNP)

answer

are the most common type of genetic variation among people.

question

The SRY gene

answer

is responsible for the initiation of male sex determination in humans.

question

Y-linked genes

answer

are those that are present in a unique region of the Y chromosome, where they cannot cross over with the X chromosome.

question

Y linked genes are

answer

These genes are transmitted from father to son to grandson.

question

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.

answer

True

question

A haleotype is

answer

a combination of alleles at adjacent locations on a chromosome that are inherited together

question

The mutations creating new Y-chromosome haplotypes were occurring at the same time as

answer

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.)

question

Neighboring populations tend to have more closely related Y chromosome than more

answer

distant populations

question

The clustering of the Y-chromosome haplotypes correspond with the

answer

spread of human settlements around the globe inferred from archaeological evidence.

question

Name the different types of inheritance of cytoplasmic organelles

answer

maternal, paternal, and biparental

question

Maternal inheritance

answer

the organelles in the offspring cells derive from those in the mother

question

Paternal inheritance

answer

the organelles in the offspring cells derive from those in the father

question

Biparental

answer

the organelles in the offspring cells derive from those in both parents

question

In most organisms, either _______ or _______ inheritance predominates.

answer

maternal, parental

question

Maternal inheritance is characteristic of

answer

mitochondrial diseases

question

Pedigree for the MERRF syndrome

answer

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.

question

Because mitochondrial DNA does not undergo recombination and is maternally inherited

answer

it can be used to trace human ancestry and migration.

question

The traits that Mendel studied were

answer

single gene traits

question

Complex traits are influenced by

answer

multiples genes as well as by the enviroment

question

Single gene traits are

answer

determined by variation and not influenced by the enviroment

question

Which are more common, Complex traits or single gene traits?

answer

Complex traits

question

What are some examples of complex traits?

answer

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

answer

measurement (height in inches, milk by the gallon, number of eggs, etc) known as quantitative traits

question

Quantitive traits

answer

are measured along a continuum with only small intervals between similar individuals.

question

By contrast, single-gene traits often appear in one of two or a few different phenotypes

answer

Ex: round vs. wrinkled seeds

question

Expression of complex traits is susceptible to

answer

lifestyle choices and other environmental factors

question

true-breeding (homozygous) strains are also called

answer

inbred lines

question

Complex traits are affected by multiple genes and as a result, the

answer

phenotype and genotype ratios observed by Mendel are not observed

question

The number of genes affecting complex traits is usually so large that

answer

different genotypes can have very similar phenotypes, making it difficult to see the effects of individual genes on a trait.

question

The phenotypes of many complex traits, including human height, conform to a

answer

normal distribution

question

Genetic and environmental effects can interact in

answer

unpredictable ways

question

This type of interaction is important because it implies that

answer

the effect of a genotype cannot be specified without knowing the environment, and the other way around.

question

These results also imply that there may be

answer

no genotype that is the "best" across a broad range of environments, and likewise no environment is "best" for all genotypes.

question

Genotype-by-environment interaction implies that the

answer

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:

answer

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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