GAMETE

A gamete (from Ancient Greek γαμέτης; translated gamete = wife, gametes = husband) is a cell that fuses with another gamete during fertilization (conception) in organisms that reproduce sexually. In species which produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual which produces the larger type of gamete—called an ovum (or egg)—and a male produces the smaller tadpole-like type—called a sperm. This is an example of anisogamy or heterogamy, the condition wherein females and males produce gametes of different sizes (this is the case in humans, the human ovum is approximately 20 times larger than the human sperm cell). In contrast, isogamy is the state of gametes from both sexes being the same size and shape, and given arbitrary designators for mating type. The name gamete was introduced by the Austrian biologist Gregor Mendel. Gametes carry half the genetic information of an individual, one chromosome of each type. In humans an ovum can only carry X chromosome (of the X and Y chromosomes) whereas a sperm can carry either an X or a Y, hence, it has been suggested that males have the control of the sex of any resulting zygote as the genotype of the sex-determining chromosomes of a male must be XY and a female XX. In other words, due to the presence of the Y chromosome exclusively in the sperm, it is that gamete alone which can determine that an offspring will be a male.

The production of gametes is termed gametogenesis, during which phase gametocytes divide by meiosis into gametes. Meiosis reduces the number of sets of chromosomes from two to one (i.e., produces haploid gametes from diploid gametocytes). Organs that produce gametes are called gonads in animals, and archegonia or antheridia in plants.