A spermatozoon or spermatozoan (pl. spermatozoa), from the ancient Greek σπέρμα (seed) and ζῷον (living being) and more commonly known as a sperm cell, is the haploid cell that is the male gamete. It joins an ovum to form a zygote. A zygote is a single cell, with a complete set of chromosomes, that normally develops into an embryo. Sperm cells contribute half of the genetic information to the diploid offspring. In mammals, the sex of the offspring is determined by the sperm cells: a spermatozoon bearing a Y chromosome will lead to a male (XY) offspring, while one bearing an X chromosome will lead to a female (XX) offspring (the ovum always provides an X chromosome). Sperm cells were first observed by a student of Antoni van Leeuwenhoek in 1677.
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