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Fertilization is the process in which two gametes, one from a male parent and another from a female parent, combine to form a zygote. The zygote is the first cell of a new individual with a complete set of chromosomes.
Gametes are specialized cells (sperm and egg) produced by parents for sexual reproduction.
A zygote is the result of fertilization, formed when two gametes fuse together.
Genetic variation refers to differences in genetic material between individuals, which arise from the combination of genes during fertilization.