The<unk>  is one of two sex chromosomes (allosomes) in therian mammals, including humans, and many other animals. The other is the<unk> . Y is normally the sex-determining chromosome in many species, since it is the presence or absence of Y that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the<unk>  contains the gene SRY, which triggers male development. The DNA in the human<unk>  is composed of about 59 million base pairs. The<unk>  is passed only from father to son. With a 30% difference between humans and chimpanzees, the<unk>  is one of the fastest-evolving parts of the human genome. The human<unk>  carries an estimated 100-200 genes, with between 45 and 73 of these being protein-coding. All single-copy Y-linked genes are hemizygous (present on only one chromosome) except in cases of aneuploidy such as XYY syndrome or XXYY syndrome.
Y chromosome
X chromosome
Ring chromosome 15
Satellite chromosome
Ring chromosome 18
Ring chromosome 22
Marker chromosome
Ethosome