A gamete is a reproductive cell such as a sperm or egg cell. When the sperm and egg come together and fertilize, a zygote is formed. Sperm move; eggs do not. The gametes, sperm and egg each contain one set (haploid) of the total number of chromosomes necessary for fertilization, and that allows the zygote to grow to maturity. The zygote contains all the chromosomes necessary. It is diploid--having both sets of chromosomes.