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This is an accepted version of this page This is the latest accepted revision, reviewed on 26 January 2025. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
The process of spermatogenesis as the cells progress from primary spermatocytes, to secondary spermatocytes, to spermatids, to Sperm Cycle of the seminiferous epithelium of the testis. Spermatocytogenesis is the male form of gametocytogenesis and results in the formation of spermatocytes possessing half the normal complement of genetic material.
Thus on this view, the adaptive advantage of meiosis is that it facilitates recombinational repair of DNA damage that is otherwise difficult to repair, and that occurs as a result of stress, particularly oxidative stress. [19] [20] If left unrepaired, this damage would likely be lethal to gametes and inhibit production of viable progeny.
As a result, double strand breaks in meiotic cells, unlike mitotic cells, do not typically lead to apoptosis, or cell death. [9] Homologous recombinational repair (HRR) of double-strand breaks occurs in mice during sequential stages of spermatogenesis but is most prominent in spermatocytes. [10]
The spermatid is the haploid male gametid that results from division of secondary spermatocytes. As a result of meiosis, each spermatid contains only half of the genetic material present in the original primary spermatocyte. Spermatids are connected by cytoplasmic material and have superfluous cytoplasmic material around their nuclei.
During spermatogenesis, each meiotic division is symmetric such that each primary spermatocyte gives rise to 2 secondary spermatocytes after meiosis I, and eventually 4 spermatids after meiosis II. Meiosis II-nondisjunction may also result in aneuploidy syndromes, but only to a much smaller extent than do segregation failures in meiosis I. [6]
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 ...
Exposure to RA drives cellular differentiation into A1 spermatogonia and is implicated in further meiotic differentiation. [4] As a result of differentiation, the genes required to maintain an SSC state are no longer expressed. [14] Male reproductive function declines with increasing age as indicated by decreased sperm quality and fertility. [25]