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McClintock used the prophase and metaphase stages of mitosis to describe the morphology of corn's chromosomes, and later showed the first ever cytological demonstration of crossing over in meiosis. Working with student Harriet Creighton, McClintock also made significant contributions to the early understanding of codependency of linked genes.
Studies in male mouse meiosis have shown that after DNA damaging treatments like gamma irradiation, two types of repair responses occur depending on the meiotic stage: [5] From leptotene to early pachytene, exogenous DNA damage triggers widespread presence of the repair protein gammaH2AX in the nucleus, associated with homologous recombination ...
This is an accepted version of this page This is the latest accepted revision, reviewed on 19 December 2024. 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 ...
As it occurs after G2 of interphase, DNA has been already replicated when prophase begins. [1] Fluorescence microscope image of two mouse cell nuclei in prophase (scale bar is 5 μm). [2] Prophase (from Ancient Greek προ- 'before' and φάσις (phásis) 'appearance') is the first stage of cell division in both mitosis and meiosis.
Zygotene (from greek "paired threads" [1]) is the second stage of prophase I during meiosis, the specialized cell division that reduces the chromosome number by half to produce haploid gametes. It follows the Leptotene stage and is followed by Pachytene stage.
Synapsis or Syzygy is the pairing of two chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis. When homologous chromosomes synapse, their ends are first attached to the nuclear envelope.
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. These chromosomes (paired chromatids) then pair with the homologous chromosome (also paired chromatids) present in the same nucleus ...
Homologous recombination is the principal mechanism of DNA repair acting during meiosis. From the leptotene to early pachytene stages of meiosis exogenous damage triggered the massive presence of gamma H2AX (which forms when DNA double-strand breaks appear), H2AX was present throughout the nucleus, and this was associated with DNA repair ...