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A germ cell is any cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm.
Meiosis (/ m aɪ ˈ oʊ s ɪ s / ⓘ; from Ancient Greek μείωσις (meíōsis) 'lessening', (since it is a reductional division) [1] [2] is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells.
In humans, on average, about 50 DNA double-strand breaks occur per cell in each cell generation. [21] Meiosis, which facilitates recombinational repair between non-sister chromosomes, can efficiently repair these prevalent damages in the DNA passed on to germ cells, and consequently prevent loss of fertility in humans.
This is followed by two cell divisions to generate haploid gametes. After the DNA is replicated in meiosis, the homologous chromosomes pair up so that their DNA sequences are aligned with each other. During this period before cell divisions, genetic information is exchanged between homologous chromosomes in genetic recombination. Homologous ...
After female (XX) germ cells collect in the undifferentiated gonads, the up-regulation of Stra8 is required for germ cell differentiation into an oogonium and eventually enter meiosis. One major factor that contributes to the up-regulation of Stra8 , is the initiation of the β-Catenin signaling pathway via RSPO1, which is also responsible for ...
Cormlets of Watsonia meriana, an example of apomixis Clathria tuberosa, an example of a sponge that can grow indefinitely from somatic tissue and reconstitute itself from totipotent separated somatic cells. In biology and genetics, the germline is the population of a multicellular organism's cells that develop into germ cells.
In mammalian germ cell development, sexually dimorphic gametes differentiates into primordial germ cells from pluripotent cells during initial mammalian development. [2] Males and females of a species that reproduce sexually have different forms of gametogenesis: spermatogenesis (male): Immature germ cells are produced in a man's testes. To ...
Meiosis in Grasshopper testes (primary spermatocytes in zygotene, pachytene, prophase I). The spermatogenesis process has been elucidated throughout the years by researchers who divided the process into multiple stages or phases, depending on intrinsic (germ and Sertoli cells) and extrinsic (FSH and LH) factors. [16]