Chapter 13 (Problem 31) To determine whether radiation associated with the atomi

Question

Chapter 13 (Problem 31) To determine whether radiation associated with the atomic bombings of Hiroshima and Nagasaki produced recessive germ-line mutations, scientists examined the sex ratio of the children of the survivors of the blasts. The best explanation for why an increase in germ-line mutations might be expected to alter the sex ratio is that

A. females will exhibit disproportionate lethality due to the presence of two X chromosomes, that is, more females than males are expected to die because of sex-linked recessive lethal mutations.

B. females will exhibit disproportionate lethality due to the lack of the Y chromosome, that is, more females than males are expected to die because of sex-linked recessive lethal mutations that are not suppressed by the Y chromosome.

C. males will exhibit disproportionate lethality due to the presence of a Y chromosome, that is, more males than females are expected to die because of sex-linked recessive lethal mutations on the Y chromosome.

D. males will exhibit disproportionate lethality due to the existence of one X chromosome, that is, more males than females are expected to die because of sex-linked recessive lethal mutations. E. A and B are correct.

Explanation / Answer

Correct answer would be:

D. males will exhibit disproportionate lethality due to the existence of one X chromosome, that is, more males than females are expected to die because of sex-linked recessive lethal mutations.

Reason:Males have one X chromosome.Therefore,for a recessive trait to be expressed, mutation of one recessive allele on the X chromosome is enough.

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