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Sister chromatid cohesion is essential for the correct distribution of genetic information between daughter cells and the repair of damaged chromosomes. Defects in this process may lead to aneuploidy and cancer, especially when checkpoints fail to detect DNA damage or when incorrectly attached mitotic spindles do not function properly.
Establishment of sister chromatid cohesion is the process by which chromatin-associated cohesin protein becomes competent to physically bind together the sister chromatids. In general, cohesion is established during S phase as DNA is replicated, and is lost when chromosomes segregate during mitosis and meiosis .
Without cohesin, the cell would be unable to control sister chromatid segregation since there would be no way of ensuring whether the spindle fiber—attached on each sister chromatid—is from a different pole. [15] [16] Other proteins modulate cohesin function by regulating this process, such as PDS5A, PDS5B, NIPBL and ESCO1 in mammalian ...
During cell division, the identical copies (called a "sister chromatid pair") are joined at the region called the centromere (2). Once the paired sister chromatids have separated from one another (in the anaphase of mitosis ) each is known as a daughter chromosome.
During mitosis, each sister chromatid forming the complete chromosome has its own kinetochore. Distinct sister kinetochores can be observed at first at the end of G2 phase in cultured mammalian cells. [17] These early kinetochores show a mature laminar structure before the nuclear envelope breaks down. [18]
In this diagram of a duplicated chromosome, (2) identifies the centromere—the region that joins the two sister chromatids, or each half of the chromosome. In prophase of mitosis, specialized regions on centromeres called kinetochores attach chromosomes to spindle fibers. The centromere links a pair of sister chromatids together during cell ...
Sister chromatid crossover events are known to occur at a rate of several crossover events per cell per division in eukaryotes. [29] Most of these events involve an exchange of equal amounts of genetic information, but unequal exchanges may occur due to sequence mismatch.
Chromosome segregation is the process in eukaryotes by which two sister chromatids formed as a consequence of DNA replication, or paired homologous chromosomes, separate from each other and migrate to opposite poles of the nucleus. This segregation process occurs during both mitosis and meiosis. Chromosome segregation also occurs in prokaryotes ...