The<unk>  is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the<unk> , and is found in both males and females. It is a part of the<unk> Y sex-determination system and<unk> O sex-determination system. The<unk>  was named for its unique properties by early researchers, which resulted in the naming of its counterpart<unk> , for the next letter in the alphabet, following its subsequent discovery.
X chromosome
Y chromosome
Ring chromosome 15
Ring chromosome 18
Ring chromosome 22
Ethosome
Dup15q
Satellite chromosome