A homogametic sex is a sex in individuals of which identical gametes are formed during meiosis , bearing the same sex chromosomes [1] . For example, in humans, a woman’s eggs (XX) contain one X chromosome , unlike male gametes, spermatozoa , which contain either the X or Y chromosome ( heterogametic sex ).
In most insects, mammals, including humans , the homogametic sex is female (XX). In birds , reptiles and butterflies , on the contrary, the homogametic sex is male (ZZ) [2] .