(August 2005) The Human Y chromosome The Y chromosome is the shortest chromosome in humans, and most of the Y chromosome is believed to be made of junk DNA. In the 1960s, Ohno proposed that the human Y chromosome is a profoundly degenerated X chromosome with very few genes on it encoding male-specific features1 and some began to speculate that the continued degradation of the Y chromosome might result in the extinction of the human male. In order to address this question, it is helpful to know the origin of the Y chromosome. Surprisingly, the most primitive Y chromosome found…