DNA polymerase occasionally incorporates the wrong nucleotide during DNA replication. If left unrepaired, the base-pair mismatch that results will lead to mutation in the next replication. As part of a template strand, the incorporated wrong base will direct the incorporation of a base complementary to itself, so the bases on both strands of the DNA at that position will now be different from what they were before the mismatch event. The MM-minus strain of yeast does not have a functional mismatch excision repair system, but it has normal base excision repair and nucleotide excision repair systems. Which of the following statements is correct about differences in the mutation spectrum between MMR-minus and wildtype yeast? More than one answer is correct. (a) More point mutations will arise in MMR-minus yeast. Fewer point mutations will arise in MMR-minus yeast as compared with wildtype. (b) Of the total point mutations that do occur, the fraction in which G is replaced by C will be lower in MMR-minus yeast than in wildtype. (Hint: imagine the very first mismatch event and ask yourself if base excision repair could handle it.) (d) Of the total point mutations that do occur, the fraction of in which G is replaced by A will be lower in MMR-minus yeast than in wildtype. (e) Of the total point mutations that do occur, the fraction in which A is replaced by G will be lower in MMR-minus yeast.

Human Heredity: Principles and Issues (MindTap Course List)

11th Edition

ISBN:9781305251052

Author:Michael Cummings

Publisher:Michael Cummings

Chapter11: Genome Alterations: Mutation And Epigenetics

Section: Chapter Questions

Problem 18QP: Replication involves a period of time during which DNA is particularly susceptible to the...

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DNA polymerase occasionally incorporates the wrong nucleotide during DNA

replication. If left unrepaired, the base-pair mismatch that results will lead to

mutation in the next replication. As part of a template strand, the incorporated

wrong base will direct the incorporation of a base complementary to itself, so the

bases on both strands of the DNA at that position will now be different from what

they were before the mismatch event.

The MM-minus strain of yeast does not have a functional mismatch excision repair

system, but it has normal base excision repair and nucleotide excision repair systems.

Which of the following statements is correct about differences in the mutation

spectrum between MMR-minus and wildtype yeast?

More than one answer is correct.

(a) More point mutations will arise in MMR-minus yeast.

Fewer point mutations will arise in MMR-minus yeast as compared with

wildtype.

(b) Of the total point mutations that do occur, the fraction in which G is replaced by

C will be lower in MMR-minus yeast than in wildtype. (Hint: imagine the very

first mismatch event and ask yourself if base excision repair could handle it.)

(d) Of the total point mutations that do occur, the fraction of in which G is replaced

by A will be lower in MMR-minus yeast than in wildtype.

(e) Of the total point mutations that do occur, the fraction in which A is replaced by

G will be lower in MMR-minus yeast.

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