Gametes are mature sexual cells with unpaired chromosomes. This gamete is the basic male or female sexual unit in reproduction. Both the egg and sperm are forms of gametes, with specialized biological structures and functions for their roles. The gametes fuse, forming a zygote as the initial cell after combination. Male gametes have chromosomes XX, whereas the female chromosome is XY. The fused chromosome is decided as male or female depending on the chromosome structure after fusion.