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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.
Being pulled in opposite directions will cause the two sister chromatids to break apart from each other, but not necessarily at the site that they fused. [4] This results in the two daughter cells receiving an uneven chromatid. [ 4 ]
Changes in patterns of sister chromatid cohesion have been observed in cases of DNA damage. Cohesin is required for repair of DNA double-strand breaks (DSBs). One mechanism of DSB repair, homologous recombination (HR), requires the presence of the sister chromatid for repair at the break site. Thus, it is possible that cohesion is required for ...
The recombinases catalyze invasion of the opposite chromatid by the single-stranded DNA from one end of the break. Next, the 3' end of the invading DNA primes DNA synthesis, causing displacement of the complementary strand, which subsequently anneals to the single-stranded DNA generated from the other end of the initial double-stranded break.
The DNA sequence of two sister chromatids is completely identical (apart from very rare DNA copying errors). Sister chromatid exchange (SCE) is the exchange of genetic information between two sister chromatids. SCEs can occur during mitosis or meiosis.
Cohesin is a protein complex that mediates sister chromatid cohesion, homologous recombination, and DNA looping. Cohesin is formed of SMC3, SMC1, SCC1 and SCC3 (SA1 or SA2 in humans). Cohesin holds sister chromatids together after DNA replication until anaphase when removal of cohesin leads to separation of sister chromatids. The complex forms ...
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]
Micrograph showing condensed chromosomes in blue, kinetochores in pink, and microtubules in green during metaphase of mitosis. In cell biology, the spindle apparatus is the cytoskeletal structure of eukaryotic cells that forms during cell division to separate sister chromatids between daughter cells.