The Y chromosome is perhaps the most puzzling part of the human genome. The team revealed the structures of sperm-regulating gene families and discovered 41 additional genes in the Y chromosome. The Y chromosome, along with the X chromosome, is often discussed for its role in sexual development. Now, using a donor with both an X and a Y chromosome, the consortium built a complete blueprint of the Y chromosome and every element of its DNA. The Johns Hopkins group compared the new Y chromosome sequence against the genetic data from thousands of people worldwide.