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The first theory rests upon the idea that meiosis evolved as another method of DNA repair, and thus crossing-over is a novel way to replace possibly damaged sections of DNA. [9] The second theory comes from the idea that meiosis evolved from bacterial transformation, with the function of propagating diversity. [9]
This is an accepted version of this page This is the latest accepted revision, reviewed on 5 January 2025. 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 ...
Meiotic recombination may begin with a double-strand break, either induced by Spo11 [2] or by other endogenous or exogenous causes of DNA damage. These DNA breaks must be repaired before metaphase I. and these DSBs must be repaired before metaphase I. The cell monitor these DSBs via ATM pathway, in which Cdc25 is suppressed when DSB lesion is ...
In prophase I of meiosis I, each chromosome is aligned with its homologous partner and pairs completely. In prophase I, the DNA has already undergone replication so each chromosome consists of two identical chromatids connected by a common centromere. [10] During the zygotene stage of prophase I, the homologous chromosomes pair up with each ...
Two of the four chromatids present early in meiosis (prophase I) are paired with each other and able to interact. Recombination, in this model, is initiated by a double-strand break (or gap) shown in the DNA molecule (chromatid) at the top of the figure. Other types of DNA damage may also initiate recombination.
The introduction of DSBs in DNA often employs the topoisomerase-like protein SPO11. [3] CO recombination may also be initiated by external sources of DNA damage such as X-irradiation, [4] or internal sources. [5] [6] There is evidence that CO recombination facilitates meiotic chromosome segregation. [2]
Mitotic recombination is primarily a result of DNA repair processes responding to spontaneous or induced damages. [2] [3] [4] Homologous recombinational repair during mitosis is largely limited to interaction between nearby sister chromatids that are present in a cell subsequent to DNA replication but prior to cell division. Due to the special ...
The formation of a bivalent occurs during the first division of meiosis (in the zygotene stage of meiotic prophase 1). In most organisms, each replicated chromosome (composed of two identical sister chromatids [1] [2]) elicits formation of DNA double-strand breaks during the leptotene phase. [3]