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How many chromosomes does a human egg cell contribute to a zygote?
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Fertilization
Fertilization occurs when a sperm cell penetrates and fuses with an egg (ovum).
A human egg cell (ovum) contributes 23 chromosomes to a zygote.1
In humans, reproductive cells are produced through a specialized process of cell division called meiosis, which reduces the number of chromosomes by half. While typical human body cells are diploid and contain 46 chromosomes, the mature egg is a haploid cell, meaning it carries a single set of 23 chromosomes.213
During the process of fertilization, the egg unites with a sperm cell, which also contributes 23 chromosomes. This fusion restores the full diploid number of 46 chromosomes in the resulting zygote, providing the genetic foundation for the new individual.12