Pros And Cons Of Homologous Recombination

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Homologous recombination (HR) can be explained as a process where DNA is exchanged or copied between two chromosomes or different regions of the same chromosome. The process requires homology between the exchanging DNA regions. Homologous recombination repairs DNA breaks, especially double stranded breaks (DSBs), stabilizes and repairs stalled forks. HR consists of a series of inter related pathways that function in repair of DNA breaks (Figure 4). Initially, stretches of single stranded DNA (ssDNA) are resected at the stalled forks or DSB ends which are quickly bound by replication protein A (RPA). Rad51 replaces RPA and binds to these ssDNA with the aid of the Rad52 mediator function (21,22). Rad51 form a nucleoprotein filament, which can…show more content…
During meiotic prophase, crossovers provide physical links between a pair of homologous chromosomes. However, meiotic crossovers are reduced around the centromere in order to prevent premature separation of sister chromatids (42). Crossovers occurring in and around the centromere can lead to lagging chromosomes due to attachment of the centromere to both spindle bodies leading to aneuploidy. The suppression of meiotic crossovers is explained by reduction of meiosis-specific DNA double-strand breaks (DSBs) around centromeres (43,44). However, non-crossover recombination occurs around centromeres in maize and budding yeast (45,46), suggesting that crossovers are selectively suppressed even after the formation of meiotic DSBs. However, the regulation of recombination and crossover between the centromere repeats in mitotic cells and whether it is differently regulated from the arm region remains unknown. It is suggested that the unique centromere chromatin that ensures faithful segregation of chromosomes may confer important roles in regulation of recombination. However, the precise role of the centromere specific chromatin in context of recombination and crossover control to maintain the genomic integrity remains elusive. It also remains to be elucidated how intrinsically unstable repeat sequences of the centromere are maintained to avoid gross chromosomal rearrangements. A specific regulatory mechanism may be important to maintain the proper structural and functional integrity of one of the most complex and critical regions of the chromosome, the

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