The Human Y Chromosome: The Biological Role of a "Functional Wasteland"

Abstract

"Functional wasteland," "Nonrecombining desert" and "Gene-poor chromosome" are only some examples of the different definitions given to the Y chromosome in the last decade. In comparison to the other chromosomes, the Y is poor in genes, being more than 50% of its sequence composed of repeated elements. Moreover, the Y genes are in continuous decay probably due to the lack of recombination of this chromosome. But the human Y chromosome, at the same time, plays a central role in human biology. The presence or absence of this chromosome determines gonadal sex. Thus, mammalian embryos with a Y chromosome develop testes, while those without it develop ovaries (Polani, 1981). What is responsible for the male phenotype is the testis-determining SRY gene (Sinclair, 1990) which remains the most distinguishing characteristic of this chromosome. In addition to SRY, the presence of other genes with important functions has been reported, including a region associated to Turner estigmata, a gene related to the development of gonadoblastoma and, most important, genes related to germ cell development and maintenance and then, related with male fertility (Lahn and Page, 1997). This paper reviews the structure and the biological functions of this peculiar chromosome.

Figure 1

Schematic representation of the Y chromosome. Genes in the two pseudoautosomal regions (PAR1 and PAR2) as well as those in the nonrecombining Y region (NRY) are illustrated.