Genetics: From Genes to Genomes
6th Edition
ISBN: 9781259700903
Author: Leland Hartwell Dr., Michael L. Goldberg Professor Dr., Janice Fischer, Leroy Hood Dr.
Publisher: McGraw-Hill Education
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Chapter 8, Problem 55P
An investigator was interested in studying UAG nonsense suppressor mutations in bacteria. In one species of bacteria, she was able to select two different mutants of this type, one in a tRNATyr gene and the other in a tRNAGln gene, but in a second species, she was not able to obtain any such nonsense suppressor mutations, even after very extensive effort. What could explain the difference between the two species?
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Geneticists often use ethylmethane sulfonate (EMS) to induce mutations in Drosophila. Why is EMS a mutagen of choice for genetic research? What would be the effects of EMS in a strain of Drosophila lacking functional mismatch repair systems?
You are studying the tryptophan synthetase gene that Yanofsky also examined to determine the relationship between the nucleotide sequence and the amino acid sequence of the gene. Yanofsky found a large number of mutations that affected the tryptophan synthetase gene.
A) If you took this mutant E. Coli line (that has an Arginine at this location) and exposed it to a mutagen that could potentially change bases, what are the second mutations you would most likely discover that would restore the activity of the tryptophan synthetase gene and where would it be located?
B) Most of the mutations that Yanofsky recovered were missense mutations. However, Yanofsky also recovered a nonsense mutation that changed amino acid number 15 into a stop codon. This codon normally encodes Lysine. Does the recovery of this mutation support the hypothesis that this Lysine residue is critical in the function of the tryptophan synthetase protein?
Most of the mutations that Yanofsky recovered were missense mutations. However, Yanofsky also recovered a nonsense mutation that changed amino acid number 15 into a stop codon. This codon normally encodes Lysine. Does the recovery of this mutation support the hypothesis that this Lysine residue is critical in the function of the tryptophan synthetase protein? Why or why not?
Chapter 8 Solutions
Genetics: From Genes to Genomes
Ch. 8 - For each of the terms in the left column, choose...Ch. 8 - Match the hypothesis from the left column to the...Ch. 8 - How would the artificial mRNA 5GUGUGUGU . . . 3 be...Ch. 8 - An example of a portion of the T4 rIIB gene in...Ch. 8 - Consider Crick and Brenners experiments in Fig....Ch. 8 - The HbSsickle-cell allele of the human -globin...Ch. 8 - The following diagram describes the mRNA sequence...Ch. 8 - The amino acid sequence of part of a protein has...Ch. 8 - The results shown in Fig. 8.5 may have struck you...Ch. 8 - Identify all the amino acid-specifying codons in...
Ch. 8 - Before the technology existed to synthesize RNA...Ch. 8 - A particular protein has the amino acid sequence...Ch. 8 - How many possible open reading frames frames...Ch. 8 - Prob. 14PCh. 8 - Charles Yanofsky isolated many different trpA-...Ch. 8 - The sequence of a segment of mRNA, beginning with...Ch. 8 - You identify a proflavin-generated allele of a...Ch. 8 - Using recombinant DNA techniques which will be...Ch. 8 - Describe the steps in transcription that require...Ch. 8 - Chapters 6 and 7 explained that mistakes made by...Ch. 8 - The coding sequence for gene F is read from left...Ch. 8 - If you mixed the mRNA of a human gene with the...Ch. 8 - Prob. 23PCh. 8 - The Drosophila gene Dscam1 encodes proteins on the...Ch. 8 - Describe the steps in translation that require...Ch. 8 - Locate as accurately as possible the listed items...Ch. 8 - Concerning the figure for Problem 26: a. Which...Ch. 8 - a. Can a tRNA exist that has the anticodon...Ch. 8 - For parts a and b of Problem 28, consider the DNA...Ch. 8 - Remembering that the wobble base of the tRNA is...Ch. 8 - Prob. 31PCh. 8 - The yeast gene encoding a protein found in the...Ch. 8 - The sequence of a complete eukaryotic gene...Ch. 8 - Arrange the following list of eukaryotic gene...Ch. 8 - Prob. 35PCh. 8 - The human gene for 2 lens crystallin has the...Ch. 8 - In prokaryotes, a search for genes in a DNA...Ch. 8 - a. The genetic code table shown in Fig. 8.2...Ch. 8 - a. Very few if any eukaryotic genes contain tracts...Ch. 8 - Explain how differences in the initiation of...Ch. 8 - Do you think each of the following types of...Ch. 8 - Null mutations are valuable genetic resources...Ch. 8 - The following is a list of mutations that have...Ch. 8 - Considering further the mutations described in...Ch. 8 - Adermatoglyphia described previously in Problem 18...Ch. 8 - Prob. 46PCh. 8 - You learned in Problem 21 in Chapter 7 that the...Ch. 8 - When 1 million cells of a culture of haploid yeast...Ch. 8 - Why is a nonsense suppressor tRNATyr, even though...Ch. 8 - A mutant B. adonis bacterium has a nonsense...Ch. 8 - You are studying mutations in a bacterial gene...Ch. 8 - Another class of suppressor mutations, not...Ch. 8 - Yet another class of suppressor mutations not...Ch. 8 - At least one nonsense suppressing tRNA is known...Ch. 8 - An investigator was interested in studying UAG...Ch. 8 - Prob. 56PCh. 8 - In certain bacterial species, pyrrolysine Pyl,...Ch. 8 - Canavanine is an amino acid similar to arginine...
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- A mutant strain of bacteria is isolated in which the amino acid glutamine is often erroneously substituted for glutamic acid during protein synthesis. What kind of mutation might be underlying this defect? How could you test this hypothesis?arrow_forwardOchre and amber are two distinct nonsense mutations. Before the genetic code was worked out, Sydney Brenner, Anthony O. Stretton, and Samuel Kaplan applied different types of mutagens to bacteriophages in an attempt to determine the bases present in the codons responsible for amber and ochre mutations. They knew that the ochre and amber mutations were suppressed by different types of suppressor mutations, which demonstrated that each is a different stop codon. They obtained the following results: (1) A single-base substitution could convert an ochre mutation into an amber mutation. (2) Hydroxylamine induced both ochre and amber mutations in wildtype phages. (3) 2-Aminopurine caused ochre to mutate to amber. (4) Hydroxylamine did not cause ochre to mutate to amber. These data do not allow the complete nucleotide sequence of the amber and ochre codons to be worked out, but they do provide some information about the bases found in the nonsense mutations. a. What conclusions about the…arrow_forwardOchre and amber are two distinct nonsense mutations. Before the genetic code was worked out, Sydney Brenner, Anthony O. Stretton, and Samuel Kaplan applied different types of mutagens to bacteriophages in an attempt to determine the bases present in the codons responsible for amber and ochre mutations. They knew that the ochre and amber mutations were suppressed by different types of suppressor mutations, which demonstrated that each is a different stop codon. They obtained the following results: (1) A single-base substitution could convert an ochre mutation into an amber mutation. (2) Hydroxylamine induced both ochre and amber mutations in wildtype phages. (3) 2-Aminopurine caused ochre to mutate to amber. (4) Hydroxylamine did not cause ochre to mutate to amber. These data do not allow the complete nucleotide sequence of the amber and ochre codons to be worked out, but they do provide some information about the bases found in the nonsense mutations. Q. Of the three nonsense codons…arrow_forward
- You are interested in studying resistance to heavy metals and have selected the yeast Saccharomyces cerevisea to conduct your studies. You have recovered a deletion mutant that does not tolerate high concentrations of zinc (grows poorly in zinc containing media ) and have designated the mutant pgz-1 (for poor growth in zinc ). (a) What is the advantage to the type of mutant used in this work? What class of mutagen was likely use to generate pgz-1? ( b) Do you expect the PGZ gene to be expressed in your mutant? Explain.arrow_forwardThe genetic alteration responsible for sickle-cell anemia in humans involves: a transition mutation from A to G, substituting glutamic acid for valine in a-globin a transversion mutation from T to A, substituting valine for glutamic acid in b-globin a transition mutation from T to C, substituting valine for glutamic acid in b-globin a transversion mutation from G to C, substituting glutamic acid for valine in a-globin a frameshift mutation of one ATC codon, removing glutamic acid from b-globinarrow_forwardYou start by looking at the mutations that Yanofsky recovered in TrpA. One of these mutations affected amino acid number 177 and changed it from Leucine to Arginine – because Yanofsky recovered it in his screen, that means that having an Arginine in this position does not allow the TrpA gene to function properly. Assuming that this particular mutation induced by Yanofsky was a single nucleotide change, what are the possible codons of Leucine that could be found at this position in wild-type TrpA? What are the possible codons for Leucine that could be found in the mutant?. If you took this mutant E. Coli line (that has an Arginine at this location) and exposed it to a mutagen that could potentially change bases, what are the second mutations you would most likely discover that would restore the activity of the tryptophan synthetase gene and where would it be located?arrow_forward
- You start by looking at the mutations that Yanofsky recovered in TrpA. One of these mutations affected amino acid number 177 and changed it from Leucine to Arginine – because Yanofsky recovered it in his screen, that means that having an Arginine in this position does not allow the TrpA gene to function properly. Assuming that this particular mutation induced by Yanofsky was a single nucleotide change, what are the possible codons of Leucine that could be found at this position in wild-type TrpA? What are the possible codons for Leucine that could be found in the mutant?arrow_forwarda. Some antibiotics, such as rifampin, interfere with the function of RNA polymerase. What biological process is rifampin disrupting? b. Some antibiotic-resistant M. tuberculosis bacteria have a single point mutation (CàT) in the rpoB gene that causes an amino acid change from serine (a polar amino acid) to leucine (a non-polar amino acid). What type of mutation is this? Do you expect this to have no effect, a small effect, or a large effect on the polypeptide produced? Explain your reasoning. c. The rpoB gene encodes a subunit of the bacterial RNA polymerase protein. The point mutation described in Question 2 causes a change in protein folding, which leads to the inability of the rifampin antibiotic to bind to the RNA polymerase. Which level(s) of protein structure is/are affected by this change?arrow_forwardWhy are frameshift mutations likely to be more detrimental than point mutations, in which a single pyrimidine or purine has been substituted?arrow_forward
- As we described in class, in the early 1960's Francis Crick and colleagues set out to determine how many nucleotide bases make up a codon, before it was possible to sequence DNA and before Nirenberg and his colleagues solved the genetic code. To do this, they used a chemical mutagen that they knew made single nucleotide changes, used this mutagen to conduct a screen for mutations that disrupted a particular gene, and collected a number of different mutations in this gene. Briefly describe the logic they used to deduce that the codon length is 3 nucleotides long.arrow_forwardConsider the tryptophan codon 5′ - UGG - 3′ in the standard genetic code . Can a single base change in this codon create a synonymous mutation? Can a single base change in this codon create a nonsense codon?arrow_forwardLet’s suppose that a vertebrate organism carries a mutation that causes some cells that normally differentiate into nerve cells to differentiate into muscle cells. A molecular analysis reveals that this mutation is in a gene that encodes a DNA methyltransferase. Explain how an alteration in a DNA methyltransferase could produce this phenotype.arrow_forward
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