Gamete Topics

• genetic recombination
• sperm cell
• anisogamy
• isogamy
• random element
• archegonia
• antheridia
• complete set of chromosomes
• human ovum
• gametes
• sexual reproduction
• zygote
• marine species
• meiosis
• distinct types
• set of chromosomes
• hybridization
• 2n
• tadpole
• hybrids

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Gamete, Gamete

In species that produce two morphologically distinct types of gametes, and in which each individual produces only one type, a female is any individual that 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.

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.

When two gametes fuse (in animals typically involving a sperm and an egg), they form a zygote a cell that has a complete set of chromosomes(2n) and therefore is diploid. The zygote receives one set of chromosomes from each of the two gametes through the fusion of the two gamete nuclei.

Since some algae and fungi have sexual reproduction by combining two identical gametes, there is no male/female distinction in these species. This raises the question as to why most large/familiar species reproduce by sperm and egg. One theory for why the male/female distinction is so common is that it facilitated encounters between gametes, in ancestral marine species. Dusenbery, David B. (2009).

They can be hybrids produced through crossover (a form of genetic recombination) of chromosomes, which takes place in meiosis. This hybridization has a random element, and the chromosomes tend to be a little different in every gamete that an individual produces. This recombination and the fact that the two chromosome sets ultimately come from either a grandmother or a grandfather on each parental side account for the genetic dissimilarity of siblings.

Source: Wikipedia > Gamete