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Chapter 7. Mutation

A common clinical feature seen in persons affected with a disorder of DNA repair is

A. albinism.

B. predisposition to cancer.

C. excess stability of the genome.

D. hyperproduction of immune globulins.

E. delayed aging.

B is the correct answer.

DNA repair abnormalities increase the risk of cancer, but produce genome instability, premature aging, and immune deficiency. Albinism is not a common feature.

A patient is suspected of having a specific medical condition. A DNA sequencing test is performed to confirm the clinical diagnosis. In the report, the laboratory says that a change in the DNA sequence was found. The report also states that this particular change has been seen in several other individuals, none of whom have had the suspected condition. The best interpretation of this is that the genetic change is a

A. normal sequence.

B. known pathogenic mutation.

C. known benign polymorphism.

D. polymorphism of unknown significance.

E. codon malalignment.

C is the correct answer.

There is a polymorphism so it is not a normal sequence. Since it has not been seen in individuals with disease it would be a known benign polymorphism. It is not pathogenic nor is it unknown. Choice E is made up.

Which is the correct statement regarding mutations?

A. Mutations are rare events.

B. Mutations occur at a rate evenly distributed across the genome.

C. Spontaneous mutations are typically more severe than induced mutations.

D. Because mutations are set in the DNA, therapy is not possible.

E. Mutations may occur in either germ-line or somatic cells.

E is the correct answer.

Mutations are common events and they are unevenly distributed across the genome (hence the term 'hot spots'). Mutations that are induced versus those that occur spontaneously are no different in their impact. As demonstrated in the clinical correlation section, therapies may be able to 'correct' a mutation.

Agents that are known to induce mutations (mutagens):

A. often are also carcinogenic (i.e., induce cancer).

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