Bio 151 Ch 16 – Flashcards
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What is the function of mRNA?
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To carry information from DNA out of the nucleus to the site of protein synthesis
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Which of the following is an exception to the central dogma of molecular biology?
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Single-stranded RNA from a virus is used as a template for producing DNA that inserts into the host genome.
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Which enzyme allows RNA to be coded into DNA?
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Reverse transcriptase
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The discovery of retroviruses and their mechanism of replication required scientists to rethink the central dogma of molecular biology. Based on this information, which of the following statements would represent an appropriate adjustment to the central dogma?
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RNA → DNA → RNA → protein
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Two individuals with different genotypes will produce __________.
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This cannot be determined
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Srb and Horowitz isolated mutant forms of Neurospora crassa that required arginine for growth. What main conclusions did they come to in their study of these mutant Neurospora?
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Each mutant gene affected only one enzyme.
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The function of RNA polymerase is to __________.
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transcribe DNA to RNA
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Translation is _____.
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the coding from mRNA to proteins
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Consider the following two mRNA molecules:
Original RNA sequence: 5' AUGACGUGUACC 3'
New RNA sequence: 5' AUGACGUUGUACC 3'
The difference between the two molecules would most likely result in which type of change in the resulting protein molecule?
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A frameshift mutation resulting in a change in the amino acid sequence
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The sequence of a polypeptide is determined by the order of codons that specify the amino acids in the polypeptide. How many different sequences of codons can specify the polypeptide sequence methionine-histidine-alanine-leucine?
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48
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Which of the following is true about the evolution of the genetic code?
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The existing genetic code is structured in a way that efficiently minimizes the phenotypic effects of small changes in DNA and errors during translation.
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Which type of mutation causes a premature termination of protein synthesis?
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Nonsense
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Proteins are made up of 20 different amino acids. How many fewer amino acids would have to be used in order to have the genetic code be made up of two-letter words?
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Four
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Howard Temin and Satoshi Mizutani discovered that the Rous sarcoma retrovirus contains the enzyme reverse transcriptase. Why would it be important for the virus to carry its own reverse transcriptase protein? Why wouldn't the virus just make it from its reverse transcriptase gene after it infects the cell?
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The retrovirus needs its reverse transcriptase to make DNA before it can use the cell's molecular machinery to make new reverse transcriptase.
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If a researcher added a polymer of synthetic DNA that contained only adenine (A) residues to a reaction containing RNA polymerase and ribonucleotide monomers, what would be the composition of the RNA polymer produced?
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The RNA polymer would contain only uracil
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In a eukaryotic cell, the DNA is enclosed in the nucleus, whereas ribosomes that make proteins are located in the cytoplasm. How does the information in DNA that specifies the amino acid sequence of a particular protein get to the cytoplasmic protein-manufacturing centers?
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Messenger RNA molecules act as the link between genes and the protein-manufacturing centers
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Beadle and Tatum proposed the one-gene, one-enzyme hypothesis based on __________.
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N. crassa knock-out mutants that lacked the ability to synthesize certain compounds
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What change in the nature of the genetic code could be possible if, instead of two sets of base pairs (A-T, G-C), there were three sets of base pairs (A-T, G-C, and X-Y)?
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The extra base pair would make it possible to have codons two bases in length rather than three.
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Which of the following best describes the genetic screen done by Srb and Horowitz to determine the metabolic pathway for arginine synthesis?
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They irradiated N. crassa cells, grew all the mutants on arginine, and then grew each mutant on medium containing a different intermediate in the arginine pathway
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Which of the following is a correct description of a knockout allele?
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A gene altered so that it no longer produces the intended proteins
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How many different amino acids would be found in a polypeptide made from translation of an RNA containing only cytosines (C) and adenines (A) in random order?
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Six
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What is the most common number of codons that specifies a single amino acid?
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Two
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A metabolic pathway synthesizes a product through a series of steps, with each step having an intermediate compound. What conclusion should be drawn when a genetic mutation in the DNA results in the production of only the first few intermediates?
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The gene that codes for the enzyme required to produce the next intermediate in the pathway is knocked out.
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Why is it possible for a point mutation to have no effect on an individual's fitness?
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The encoded protein may be unchanged due to the redundancy of the genetic code
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How many amino acids are represented in the genetic code by just one codon?
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Two
