Towards a complete sequence of the human Y chromosome

Abstract

A few dozen genes are known on the human Y chromosome. The completion of the human genome sequence will allow identification of the remaining loci, which should shed further light on the function and evolution of this peculiar chromosome.

Figure 1

A proposed path for the evolution of the human sex chromosomes. Lahn and Page [6] postulate four inversions on the human Y chromosome, which suppressed recombination between the 'proto' sex chromosomes. Each inversion (designated 1-4) is thought to have reduced the size of the pseudoautosomal region (white) and enlarged the non-recombining portions of the X (yellow) and Y (blue) chromosomes. Time points at which the human X and Y may have diverged from the sex chromosomes of other mammals are indicated.

Figure 2

Genetic map of the non-recombining region of the human Y chromosome. The human Y chromosome consists of a large non-recombining region (NRY, which consists roughly of 24 megabases (Mb) euchromatin and 30 Mb heterochromatin) flanked by short pseudoautosomal regions (PAR, about 2.6 Mb and 0.4 Mb, respectively). Genes specific to the Y chromosome are indicated on the left-hand side of the diagram, and genes with homologs on the X chromosome are on the right-hand side. Ubiquitously expressed genes are shown in yellow, testis-specific genes are in blue, tooth-bud-specific genes in green, and brain-specific genes in red. Some testis-specific gene families have additional locations on the NRY not shown (m: multiple copies). The extensive region of Y-chromosomal heterochromatin is indicated by the grey area. The NRY is divided into intervals (as indicated by numbers on the chromosome), defined by naturally occurring deletions.