AP BIOLOGY

Detailed explanation-1: -The Y chromosome contains few genes. Most of the DNA is male specific and the remainder is autosomal. The Y chromosome encodes at least 27 proteins, some of which are confined to testis and some of which are more widely expressed (Skaletsky et al., 2003).

Detailed explanation-2: -But while the X chromosome has remained large throughout evolution, with about 2000 genes, the Y chromosome lost most of its genetic material early in its evolution; it now retains less than 100 of those original genes.

Detailed explanation-3: -The Y chromosome contains a “male-determining gene, ” the SRY gene, that causes testes to form in the embryo and results in development of external and internal male genitalia. If there is a mutation in the SRY gene, the embryo will develop female genitalia despite having XY chromosomes.

Detailed explanation-4: -The Y chromosome is important in determining a person’s biological gender. But it has much less of a say in someone’s genetic makeup, since the X chromosome likely has more than 1, 000 genes whereas the Y chromosome has fewer than 80.

Detailed explanation-5: -Typically, genes from the mother and father are shuffled-or, “cross over”-to produce a genetic combination unique to each offspring. But the Y chromosome does not undergo crossing over, and, as a result, its genes tend to degenerate, while repetitive DNA sequences accumulate.