In humans, SRY is located near a pseudoautosomal region (PAR) of the Y chromosome, a region of homology between the X and Y chromosomes that allows them to synapse during meiosis in males and is a region of crossover between the chromosomes. The diagram below shows SRY in relation to the pseudoautosomal region.

About 1 in every 25,000 newborn infants is born with sex reversal; the infant is either an apparent male but with two X chromosomes or an apparent female but with an X and a Y chromosome. Explain the origin of sex reversal in human males and females involving the SRY gene. (Hint: See Experimental Insight 3.1 for a clue about the mutational mechanism.)