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Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes.Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis.
Two single-celled haploid gametes, each containing n unpaired chromosomes, fuse to form a single-celled diploid zygote, which now contains n pairs of chromosomes, i.e. 2n chromosomes in total. [ 17 ] The single-celled diploid zygote germinates, dividing by the normal process ( mitosis ), which maintains the number of chromosomes at 2 n .
diplontic life cycle — the diploid stage is multicellular and haploid gametes are formed, meiosis is "gametic". haplodiplontic life cycle (also referred to as diplohaplontic, diplobiontic, or dibiontic life cycle) — multicellular diploid and haploid stages occur, meiosis is "sporic". The cycles differ in when mitosis (growth) occurs.
A gamete (/ ˈ ɡ æ m iː t /; from Ancient Greek γαμετή (gametḗ) 'wife', ultimately from Ancient Greek γάμος (gámos) 'marriage') is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. [1] Gametes are an organism's reproductive cells, also referred to as sex cells. [2]
Animals have life cycles with a single diploid multicellular phase that produces haploid gametes directly by meiosis. Male gametes are called sperm, and female gametes are called eggs or ova. In animals, fertilization of the ovum by a sperm results in the formation of a diploid zygote that develops by repeated mitotic divisions into a diploid ...
Bryophytes reproduce sexually, but the larger and commonly-seen organisms are haploid and produce gametes. The gametes fuse to form a zygote which develops into a sporangium, which in turn produces haploid spores. The diploid stage is relatively small and short-lived compared to the haploid stage, i.e. haploid dominance. The advantage of ...
Most species can reproduce both sexually and asexually, alternating between haploid and diploid forms. This contrasts with most multicellular eukaryotes, such as mammals, where the adults are usually diploid and produce haploid gametes which combine to form the next generation. In fungi, both haploid and diploid forms can reproduce – haploid ...
Polyploidy is especially common in plants. Most eukaryotes have diploid somatic cells, but produce haploid gametes (eggs and sperm) by meiosis. A monoploid has only one set of chromosomes, and the term is usually only applied to cells or organisms that are normally diploid. Males of bees and other Hymenoptera, for example, are monoploid.