Y Map

 
Y map: The array of genes on the Y chromosome.

Once thought to be a genetic wasteland, the Y now is known to contain at least 20 genes. Some of these genes are unique to the Y including the Y-chromosome sex-determining region and male fitness genes that are active only in the testis and are thought responsible for the formation of sperm. Other genes on the Y have counterparts on the X chromosome, are active in many body tissues and play crucial "housekeeping" roles within the cell.