Y‐chromosome‐linked Traits


Male mammals have a single X and a Y chromosome. The Y chromosome is small, containing a lot of repeated sequences and few active genes, but carries a sex‐determining factor, which determines maleness, as well as other male‐specific functions such as steps in spermatogenesis. Molecular work suggests that the Y is best understood in terms of its evolutionary history.

Keywords: sex chromosomes; pseudoautosome regions; sex determination; spermatogenesis; testis determining factor; HY antigen; Y chromosome evolution

Figure 1.

The human Y chromosome is divided into two ‘arms’ by the centromere. There are small pseudoautosomal regions (pale green) at the tips of the short and long arms. About half of the long arm is composed of highly repeated ‘junk’ DNA (pink). The rest of the differential region (mid green) contains about 20 known genes; some present in many copies.

The position of the testis‐determining gene was pinpointed within a critical sex‐determining region (dark green) on the short arm by deletion analysis in patients with different parts of the Y chromosome missing (vertical lines). If this region is deleted, the patient is a sex reversed (XY) female. SRY was cloned from this region.

The position of the spermatogenesis gene(s) was also pinpointed within a critical azoospermia region (dark green) on the long arm, by deletion analysis in patients who are oligospermic (make few sperm) or azoospermic (no sperm). This region contains RBM, one of several candidates for a spermatogenesis gene.

Figure 2.

Ancient and added regions of the mammalian X and Y chromosomes. The ancient region (blue) is conserved on the X and Y chromosomes of all therian mammals (XCR and YCR), and contains at least four X‐Y shared genes including SRY, SMCY and RBM. The added regions (pink, XAR and YAR) are autosomal in marsupial and monotreme mammals, and were therefore added since marsupials diverged from eutherians 150 million years ago.


Further Reading

Chandley A (1995) The genetic basis of male infertility. Reproductive Medicine Review 4: 1–8.

Goodfellow PN and Lovell‐Badge F (1993) SRY and sex determination in mammals. Annual Review of Genetics 27: 71–92.

Graves JAM (1995) The origin and function of the mammalian Y chromosome and Y‐borne genes ‐ an evolving understanding. BioEssays 17: 311–320.

Graves JAM (1998) Evolution of the mammalian Y chromosome and sex determining genes. Journal of Experimental Zoology 281: 472–481.

Jobling MA and Tyler‐Smith C (1995) Fathers and sons: the Y chromosome and human evolution. Trends in Genetics 11: 449–456.

Koopman P, Gubbay J, Vivian N, Goodfellow PN and Lovell‐Badge R (1991) Male development of chromosomally female mice transgenic for SRY. Nature 351: 117–121.

Lahn BT and Page DC (1997) Functional coherence of the human Y chromosome. Science 278: 675–680.

Ohno S (1967) Sex Chromosomes and Sex Linked Genes. Berlin: Springer Verlag.

Scott DM, Ehrmann IE, Ellis PS et al. (1995) Identification of a mouse male‐specific transplantation antigen, HY. Nature 376: 695–698.

Sinclair AH, Berta P, Palmer MS et al. (1990) A gene from the human sex‐determining region encodes a protein with homology to a conserved DNA‐binding motif. Nature 346: 240–244.

Sinclair AH (1998) Human sex determination. Journal of Experimental Zoology 281: 501–505.

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Graves, Jennifer A Marshall(Apr 2001) Y‐chromosome‐linked Traits. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1038/npg.els.0001459]