To determine whether radiation associated with the atomic bombings of Hiroshima

Question

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 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. 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. 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. 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.. Answers A and B are both correct.

Explanation / Answer

Answer is d.

Lethal recessive mutations of X chromosome are bound to alter sex ratio in favour of females if mothers were exposed to radiation i.e. more males are expected to die. Due to one copy of X chromosome, lethal mutations are not suppressed by the Y chromosome in males, while the other dominant X chromosome in females suppresses the mutation.

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