Zygote

A zygote is formed when two gametes unite - usually a mother's egg and a father's sperm, through sexual reproduction.

In humans, each parental unit donates 23 chromosomes in their haploid gametes which combine to give the zygote (future offspring) 46 chromosomes (except in cases of non-disjunction) and create a diploid cell that is genetically unique from the parent cells.