AP BIOLOGY ESSAY QUESTION DNA (TAB 4) – Flashcards
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Describe the steps of protein synthesis, beginning with the attachment of messenger RNA molecule to the small subunit of a ribosome and ending with the release of the polypeptide from the ribosome. Include in your answer a discussion of how different types of RNA function in the process.
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In protein synthesis, the first step is the transcription of mRNA from a DNA gene in the nucleus. Messenger RNA is read from the gene for that protein by base pairing. The order of nucleotides in mRNA determine the order of amino acids, which control what the gene codes for. Transcription occurs in the nucleus of eukaryotic cells. For every gene there is a coding strand of DNA and a "dummy" strand. Both strands are located randomly on the DNA molecule. The locations of these strands are determined by the evolutionary origins of their chromosomes. Only the coding strand will be translated into RNA base pairing. RNA polymerase is the enzyme that arranges DNA into RNA. The RNA polymerase builds the RNA strand from the 5' to the 3' end. Eukaryotes have 3 types of RNA polymerase. RNA polymerase recognizes an area in DNA called the promoter and binds to it. The promoter is a string of nucleotides in DNA to which RNA polymerase binds. Promoters signal the beginning of a gene. When the RNA polymerase binds to a promoter, its starts transcribing DNA into RNA. The mRNA is then read into protein on the ribosomes. Protein is made on a ribosome. A ribosome has a large subunit and a small subunit. The large subunit contains 2 RNA molecules ( one large, one small), while the small subunit contains 1 RNA molecule. The large subunit has three sites that can hold an amino acid: the A site, the P site, and the E site. The next step is initiation, this is when the small subunit of the ribosome attaches to an mRNA molecule. The large ribosomal subunit attaches to the mRNA-formyl methionine complex with the formylmethionine tRNA going into the P site of the large subunit. Next proteins bring all the components together. Elongation is the next process to occur. A second tRNA with its amino acid goes into the A site of the large ribosomal subunit.A peptide bond is formed between the first two amino acids. The tRNA in site P, moves to the E site and exits the cell. The tRNA in the A site moves into the P site. The next tRNA moves into the A site and another peptide bond is formed. This process continues adding one amino acid at a time. Finally termination occurs, this happens when the ribosome reaches one of the three termination codons which are : UAA, UAG, UGA. At this point the protein is released from the ribosome and the ribosomal subunits separate and move to find more mRNA.
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Describe the biochemical composition, structure and replication of DNA. Discuss how recombinant DNA techniques may be used to correct a point mutation.
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DNA is deoxyribonucleic acid, which is found in chromosomes, contains inherited information, they are made up of nucleotides, and are what make up genes. A nucleotide is composed of a sugar (deoxyribose), a phosphate group, and a base. There are 4 bases found in DNA, Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). Adenine and guanine are double ring bases while thymine and cytosine are single ring bases. Nucleotides are joined to each other by covalent bonds between the phosphate group of one nucleotide and the 3' carbon atom of the deoxyribose (sugar) of the next nucleotide. Each DNA molecule is unique because the order of nucleotides is unique. The order of nucleotides determines the order of amino acids in a protein. In order for DNA to replicate the initiator proteins must recognize a DNA sequence. Helicases break the hydrogen bonds between the two strands of nucleotides so that the strands can be separated. Then DNA polymerase adds new nucleotides to each strand. DNA needs to be very accurate or else there will be errors in the proteins. There are 50 known repair enzymes and they will repair the DNA after it replicated. Point mutation is when there is a change in a single base pair. These changes (depending on the type) can have no to a very drastic effect on the resulting protein. But the repair enzymes correct these mutations throughout the process.
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Experiments by the following scientists provided critical information concerning DNA. Describe each classical experiment and indicate how it provided evidence for the chemical nature of the gene. a)Hershey Chase- bacteriophage replication b)Griffith and Avery, MacLeod and McCarty- bacterial transformation c)Meselson and Stahl- DNA replication in bacteria
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a)Describe in a brief paragraph the characteristics of mutation. b)List the various alterations in the hereditary material that result in mutation. Illustrate each with a simple but appropriate diagram and/or example. c)Discuss how one of the alterations you discussed in part B cause hereditary change.
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Proteins-large complex molecules- are major building blocks of all living organisms. Discuss the following in relation to proteins. a)The chemical composition and levels of structure of proteins. b)The roles of DNA and RNA in protein synthesis. c)The roles of proteins in membrane structure and transport of molecules across the membrane.
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a)The chemical composition and levels of structure of proteins. A protein is a string of amino acids held together by a peptide bond. Every protein has free amino and a free carboxyl end. Typically proteins have a primary, secondary, and tertiary structure. The primary structure is the order of the amino acids in the protein. The secondary structure has the long string of amino acids coiling into an alpha helix. The tertiary structure is composed of the beta-pleated sheets and the alpha helices folding together. b)The roles of DNA and RNA in protein synthesis. DNA is deoxyribonucleic acid, which is found in chromosomes, contains inherited information, they are made up of nucleotides, and are what make up genes. A nucleotide is composed of a sugar (deoxyribose), a phosphate group, and a base. There are 4 bases found in DNA, Adenine (A), Thymine (T), Guanine (G), and Cytosine (C). Adenine and guanine are double ring bases while thymine and cytosine are single ring bases. Nucleotides are joined to each other by covalent bonds between the phosphate group of one nucleotide and the 3' carbon atom of the deoxyribose (sugar) of the next nucleotide. Each DNA molecule is unique because the order of nucleotides is unique. The order of nucleotides determines the order of amino acids in a protein. RNA is a nucleic acid composed of nucleotides and consists of one strand of nucleotides. There are three different types of RNA: Ribosomal, Messenger, and Transfer. Ribosomal RNA is the RNA molecules found in ribosomes. The large subunit RNA contains the enzymatic activity that makes the peptide bonds between amino acids. Messenger RNA is what controls the order of amino acids in a protein and determines which gene it codes for. Transfer RNA brings amino acids to ribosomes. The transfer RNA has two recognition sites: one recognizes an amino acid and the other recognizes one codon. The transfer RNA brings the the correct amino acid to the ribosome. c) not done yet
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Scientists seeking to determine which molecule is responsible for the transmission of characteristics from one generation to the next knew that the molecule must (1) copy itself precisely, (2) be stable but able to be changed, and (3) be complex enough to determine the organism's phenotype. a)Explain how DNA meets each of the three criteria stated above. b)Select one of the criteria stated above and describe experimental evidence to determine that DNA is the hereditary material.
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A portion of a specific DNA molecule consists of the following sequence of nucleotide triplets. TAC GAA CTT GGG TCC This DNA sequence codes for the following short polypeptide. methionine-leucine-glutamic acid-proline- arginine Describe the steps in the synthesis of this polypeptide. What would be the effect of a deletion or an addition in one of the DNA nucleotides? What would be the effect of a substitution in one of the nucleotides?
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Information transfer is fundamental to all living organisms. For two of the following examples, explain in detail how the transfer of information is accomplished. a)The genetic material in one eukaryotic cell is copied and distributed to two identical daughter cells. b)A gene in a eukaryotic cell is transcribed and translated to produce a protein. c)The genetic material from one bacterial cell enters another via transformation, transduction, or conjugation.
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A bacterial plasmid is 100 kb in length. The plasmid DNA was digested to completion with two restriction enzymes in three separate treatments: EcoRI, HaeIII, and EcoRI + HaeIII (double digest). The fragments were then separated with electrophoresis, as shown. Using the circle provided, construct a labeled diagram of the restriction map of the plasmid. Explain how you developed your map. Describe how: recombinant DNA technology could be used to insert a gene interest into a bacterium recombinant bacteria could be defined expression of the gene of interest could be ensured Discuss how a specific genetically modified organism might provide a benefit for humans and at the same time pose as a threat to a population or ecosystem.
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The flow of genetic information from DNA to protein in eukaryotic cell is called the central dogma of biology. Explain the role of each of the following in protein synthesis in eukaryotic cells. -RNA polymerase -Spliceosomal ( snRNPs) -Codons -tRNA
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Information flow in cells can be regulated by various mechanisms. a)Describe the role of THREE of the following in the regulation of protein synthesis: -RNA splicing -repressor proteins -methylation -siRNA b)Information flow can be altered by mutation. Describe THREE different types of mutation and their effect on protein synthesis. c)Identify TWO environmental factors that increase the rate in an organism, and discuss their effect on the genome of the organism. d)Epigenetics is the study of heritable changes in the phenotype caused by mechanisms other than changes in the DNA sequence. Describe ONE example of epigenetic inheritance.
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