chromosome

A cellular structure containing genes. Chromosomes are composed of DNA and proteins. Humans have 23 pairs of chromosomes in each body cell, one of each pair from the mother and the other from the father. The 23rd chromosome pair in males is the sex chromosome and contains an X and a Y. It is the Y chromosome (Ycs) that determines the male gender. The Y chromosome has the unique property of being passed virtually unchanged from generation to generation (only from one male to another male). This means that a man and all his sons will have the same Y chromosome. Likewise, he will have the same Y chromosome as his father and grandfather and so one. Therefore, one's profile, or haplotype, not only identifies him, but is also links him to his direct paternal line (pedigree).