The ‘weird’ male Y chromosome has finally been fully sequenced. Can we now understand how it works, and how it evolved?

The Y chromosome is a never-ending source of fascination because it bears genes that determine maleness and make sperm. The findings provide a solid base to explore how genes for sex and sperm work, how the Y chromosome evolved, and whether – as predicted – it will disappear in a few million years. These include SRY, a few genes required to make sperm, and several genes that seem to be critical for life – many of which have partners on the X. This “junk DNA” is comprised of highly repetitive sequences that derive from bits and pieces of old viruses, dead genes and very simple runs of a few bases repeated over and over. They will look for sequences that might control how SRY and the sperm genes are expressed, and to see whether genes that have X partners have retained the same functions or evolved new ones.