enow.com Web Search

Search results

  1. Results from the WOW.Com Content Network
  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. Pachytene - Wikipedia

    en.wikipedia.org/wiki/Pachytene

    Each chromosome consists of two closely associated sister chromatids along their entire length. The chromosomes appear as distinct, well-defined threadlike structures under the microscope. [3] [4] Sex chromosomes, however, are not wholly identical, and only exchange information over a small region of homology called the pseudoautosomal region. [5]

  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. Origin and function of meiosis - Wikipedia

    en.wikipedia.org/wiki/Origin_and_function_of_meiosis

    The two chromosomes which pair are referred to as non-sister chromosomes, since they did not arise simply from the replication of a parental chromosome. Recombination between non-sister chromosomes at meiosis is known to be a recombinational repair process that can repair double-strand breaks and other types of double-strand damage. [ 2 ]

  7. Chromosomal crossover - Wikipedia

    en.wikipedia.org/wiki/Chromosomal_crossover

    It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosis during a process called synapsis. Synapsis begins before the synaptonemal complex develops and is not completed until near the end of prophase I. Crossover usually occurs when matching regions on matching chromosomes break and ...

  8. 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

  9. 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 ]