A normal human gamete, sperm or ovum, carries a set of 23 chromosomes, each member of the set differing from all others in size, centromere placement, banding pattern, and gene content. When sperm and ovum unite, the resulting zygote will have two identical sets (except for the XY pair in males), 23 pairs of chromosomes. The gamete, with only one set of chromosomes, is said to be haploid (from the Greek haploos; single); the zygote, with its two sets, diploid.
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