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  2. Bivalent (genetics) - Wikipedia

    en.wikipedia.org/wiki/Bivalent_(genetics)

    A tetrad is the association of a pair of homologous chromosomes (4 sister chromatids) physically held together by at least one DNA crossover. This physical attachment allows for alignment and segregation of the homologous chromosomes in the first meiotic division. In most organisms, each replicated chromosome (composed of two identical sisters ...

  3. Homologous chromosome - Wikipedia

    en.wikipedia.org/wiki/Homologous_chromosome

    A pair of homologous chromosomes, or homologs, is a set of one maternal and one paternal chromosome that pair up with each other inside a cell during fertilization. Homologs have the same genes in the same loci , where they provide points along each chromosome that enable a pair of chromosomes to align correctly with each other before ...

  4. Sister chromatids - Wikipedia

    en.wikipedia.org/wiki/Sister_chromatids

    A pair of sister chromatids is called a dyad. A full set of sister chromatids is created during the synthesis phase of interphase, when all the chromosomes in a cell are replicated. The two sister chromatids are separated from each other into two different cells during mitosis or during the second division of meiosis.

  5. 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 .

  6. Chiasma (genetics) - Wikipedia

    en.wikipedia.org/wiki/Chiasma_(genetics)

    When each tetrad, which is composed of two pairs of sister chromatids, begins to split, the only points of contact are at the chiasmata. The chiasmata become visible during the diplotene stage of prophase I of meiosis , but the actual "crossing-overs" of genetic material are thought to occur during the previous pachytene stage.

  7. Homologous somatic pairing - Wikipedia

    en.wikipedia.org/wiki/Homologous_somatic_pairing

    The first review of somatic pairing was made by Metz in 1916, [1] citing the first descriptions of pairing made in 1907 [6] and 1908 by N. M. Stevens in germline cells, who noted: [7] “it may therefore be true that pairing of homologous chromosomes occurs in connection with each mitosis throughout the life history of these insects” (p.215)

  8. Leptotene stage - Wikipedia

    en.wikipedia.org/wiki/Leptotene_stage

    A key event is the initiation of synapsis between homologous chromosomes, which carry the same genetic information but may have different allelic variations. The homologous chromosomes begin pairing and association along their lengths, facilitated by lateral (axial) elements of the synaptonemal complex protein structure that forms between the ...

  9. Chromosome segregation - Wikipedia

    en.wikipedia.org/wiki/Chromosome_segregation

    In a diploid cell there are two sets of homologous chromosomes of different parental origin (e.g. a paternal and a maternal set). During the phase of meiosis labeled “interphase s” in the meiosis diagram there is a round of DNA replication, so that each of the chromosomes initially present is now composed of two copies called chromatids .