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  2. Meiosis - Wikipedia

    en.wikipedia.org/wiki/Meiosis

    Meiosis I segregates homologous chromosomes, which are joined as tetrads (2n, 4c), producing two haploid cells (n chromosomes, 23 in humans) which each contain chromatid pairs (1n, 2c). Because the ploidy is reduced from diploid to haploid, meiosis I is referred to as a reductional division .

  3. Sex-determination system - Wikipedia

    en.wikipedia.org/wiki/Sex-determination_system

    During meiosis, 5 of X form one chain, and 5 of Y form another chain. Thus, they behave effectively as a typical XY chromosomal system, except each of X and Y is broken into five parts, with the effect at recombinations occur very frequently at 4 particular points. [ 17 ]

  4. Sexual reproduction - Wikipedia

    en.wikipedia.org/wiki/Sexual_reproduction

    In the first stage of sexual reproduction, meiosis, the number of chromosomes is reduced from a diploid number (2n) to a haploid number (n). During fertilisation, haploid gametes come together to form a diploid zygote, and the original number of chromosomes is restored.

  5. Homologous chromosome - Wikipedia

    en.wikipedia.org/wiki/Homologous_chromosome

    So, humans have two sets of 23 chromosomes in each cell that contains a nucleus. One set of 23 chromosomes (n) is from the mother (22 autosomes, 1 sex chromosome (X only)) and one set of 23 chromosomes (n) is from the father (22 autosomes, 1 sex chromosome (X or Y)). Ultimately, this means that humans are diploid (2n) organisms. [2]

  6. Cell division - Wikipedia

    en.wikipedia.org/wiki/Cell_division

    Cell division in prokaryotes (binary fission) and eukaryotes (mitosis and meiosis). The thick lines are chromosomes, and the thin blue lines are fibers pulling on the chromosomes and pushing the ends of the cell apart. The cell cycle in eukaryotes: I = Interphase, M = Mitosis, G 0 = Gap 0, G 1 = Gap 1, G 2 = Gap 2, S = Synthesis, G 3 = Gap 3.

  7. Pachytene - Wikipedia

    en.wikipedia.org/wiki/Pachytene

    The pachytene stage (/ˈpækɪtiːn/ PAK-i-teen; from Greek words meaning "thick threads". [1]: 27 ), also known as pachynema, is the third stage of prophase I during meiosis, the specialized cell division that reduces chromosome number by half to produce haploid gametes.

  8. Chromosome segregation - Wikipedia

    en.wikipedia.org/wiki/Chromosome_segregation

    Chromosome segregation is the process in eukaryotes by which two sister chromatids formed as a consequence of DNA replication, or paired homologous chromosomes, separate from each other and migrate to opposite poles of the nucleus. This segregation process occurs during both mitosis and meiosis. Chromosome segregation also occurs in prokaryotes ...

  9. Leptotene stage - Wikipedia

    en.wikipedia.org/wiki/Leptotene_stage

    During the leptotene stage, the duplicated chromosomes - each consisting of two sister chromatids - condense from diffuse chromatin into long, thin strands that are more visible within the nucleoplasm (nucleus contents). The chromosomes become visible as thin threadlike structures known as leptonema under a light microscope. [1]: 27 [2]: 353