The y chromosome is the male sex chromosome. It is the only chromosome that is different to its homologous partner. It is the smallest chromosome of all. The y determines the maleness of the default female embryo and ensures its male development.
The X and Y are the genetic combination available in human and other mammal's sex chromosome. The XX combination denotes female formation, whereas, the XY denotes the male combination. Hence we can see that the Y chromosome is the sex-determining chromosome available in males. Actually it is the master key which determines whether an embryo would be converted into a male. Without the presence of this gene, the female would be born. This implies that femaleness is the default programme of the gene. In Klinefelter syndrome, a rare condition, a man is developed with two X and one Y chromosomes, that is, the genetic combination is XXY. In Turner syndrome, women are born with either three X (i.e., XXX) or a single X and no Y (i.e., X or X0). The ZW combination of sex chromosome is the mirror combination or reverse combination of the XY combination. This implies that in such case, females have ZW combination, whereas males have same kind of chromosomes such as ZZ. This type of combination is generally found in insects and birds.
