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:

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 one 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. Both A and B are correct.f

Answer 1

An increase in germ-line mutations might be expected to alter the sex ratio because human males are more likely to be affected by X-linked recessive mutations due to their single X chromosome, leading to a disproportionate lethality among males.

Step-by-step explanation:

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. An increase in germ-line mutations might be expected to alter the sex ratio due to X-linked recessive lethal mutations. Since human males have only one X chromosome and therefore need to inherit only one recessive mutant X allele to be affected, X-linked disorders are disproportionately observed in males. Males would exhibit disproportionate lethality due to the existence of only one X chromosome, while females, having two X chromosomes, are typically carriers when they carry one recessive X-linked allele and can still function unless they receive two copies of the recessive allele, one from each parent.