A chemist synthesizes four new chemical compounds in the laboratoryand names them PFI1, PFI2, PFI3, and PFI4. He gives the PFIcompounds to a geneticist friend and asks her to determine theirmutagenic potential. The geneticist finds that all four are highlymutagenic. She also tests the capacity of mutations produced by the PFIcompounds to be reversed by other known mutagens and obtains thefollowing results. What conclusions can you make about the nature ofthe mutations produced by these compounds?Reversed byMutations,Nitrous,Aminopurine acidAcridineorange2-producedbyHydroxylaminePFI1YesYesSomeNoPFI2NoNoNoNoPFI3YesYesNoNoPFI4NoNoNoYes

A gene mutation is alteration in the DNA sequence that make up the gene such that sequence differs…

Answered: A chemist synthesizes four new chemical…

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter15: Genomes And Genomics

Section: Chapter Questions

Problem 14QP

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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.
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?
Describe the three general groups of chemical mutagens.
A certain compound that is an analog of the base cytosinecan become incorporated into DNA. It normally hydrogen bonds just as cytosine does, but it quite often isomerizes to a form that hydrogen bonds as thymine does. Doyou expect this compound to be mutagenic, and, if so,what types of changes might it induce at the DNA level?
How do we know that many cancer-causing agents (carcinogens)are also mutagenic?
The Ames test uses the reversion rate (His− to His+)to test compounds for mutagenicity.a. Is it possible that a known mutagen, like proflavin,would be unable to revert a particular His− mutantused in the Ames test? How do you think that theAmes test is designed to deal with this issue?b. Can you think of a way to use forward mutation(His+ to His−) to test a compound for mutagenicity? (Hint: Consider using the replica plating technique in Fig. 7.6.)c. Given that the rate of forward mutation is so muchhigher than the rate of reversion, why does the Amestest use the reversion rate to test for mutagenicity?
During an Ames test, bacteria were exposed to a potential mutagen.Also, as a control, another sample of bacteria was not exposedto the mutagen. In both cases, 10 million bacteria were plated andthe following results were obtained:No mutagen: 17 coloniesWith mutagen: 2017 coloniesCalculate the mutation rate in the presence and absence of the mutagen.How much does the mutagen increase the rate of mutation?
How does a mutagen induce mutation ?explain with examples?
You are studying mutations in a bacterial gene thatcodes for an enzyme whose amino acid sequence isknown. In the wild-type protein, proline is the fifthamino acid from the amino terminal end. In one ofyour mutants with nonfunctional enzyme, you find aserine at position number 5. You subject this mutant tofurther mutagenesis and recover three different strains.Strain A has a proline at position number 5 and actsjust like a wild-type strain. Strain B has tryptophanat position number 5 and also acts like wild type.Strain C has no detectable enzyme function at anytemperature, and you can’t recover any protein thatresembles the enzyme. You mutagenize strain C andrecover a strain (C-1) that has enzyme function. Thesecond mutation in C-1 that is responsible for therecovery of enzyme function does not map at theenzyme locus.a. What is the nucleotide sequence in both strands ofthe wild-type gene at this location?b. Why does strain B have a wild-type phenotype? Whydoes the original mutant with…
Which of the following types of physical mutagens produces thymine dimmer mutations? A- gamma rays B- X-rays C- ionizing radiation D- ultraviolet light E- microwave
What percentage of the DNA in the genome actually corresponds to genes? How much is actually protein-coding exons? What makes up the rest?
Two types of mutations discussed in this chapter are (1) nucleotide changes and (2) unstable genome regions that undergo dynamic changes. Describe each type of mutation.

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