Question

What causes de la Chapelle syndrome (XX male syndrome)? A. It is caused by two nondisjunction events. The first occurs during meiosis in the mother resulting in an XX egg, and the second occurs during meiosis in the father resulting in a sperm with no X or Y chromosomes. When this sperm fertilizes the egg it results in XX male syndrome. B. SRY is intact but the body is unable to respond to the hormone androgen, which produces the female appearance. C. It is caused by unequal crossing over between the X and Y chromosomes during meiosis in the father, which results in the X chromosome containing the normally-male SRY gene. D. The SRY gene is mutated causing it to not function resulting in a male phenotype.

Answer 1

Correct answer is -

C - It is caused by unequal crossing over between the X and Y chromosomes during meiosis in the father; which results in the X Chromosomes containing the normally - male SRY gene.

EXPLANATION-

The SRY gene plays an important role in sex determination by initiating testicular development. In most XX Males the SRY gene is present . The tip of the Y chromosome contain the SRY gene and during recombination, a translocation occurs in which SRY gene on the Y chromosome is moved to become part of an X chromosome. The presence of the translocated SRY gene leads to an XX embryo developing male characters.