Human Y and X chromosomes :)The Y chromosome has the least amount of genes in all the human genome. With a 30% difference between humans and chimpanzees, the Y chromosome is one of the fastest evolving parts of the human genome. To date, over 200 Y-linked genes have been identified. All Y-linked genes are expressed and (apart from duplicated genes) hemizygous (present on only one chromosome) except in the cases of aneuploidy such as XYY syndrome or XXYY syndrome