What protein holds the sister chromatids together? During mitosis how are the sister chromatids separated? include the names of proteins involved and how the proteins mediate these two processes
The correct answer and explanation is:
The protein that holds sister chromatids together is cohesin. Cohesin is a protein complex that forms rings around the chromatids during the early stages of cell division. This helps ensure that the sister chromatids remain attached until the appropriate moment in mitosis when they need to be separated.
During mitosis, the separation of sister chromatids happens in the anaphase stage. This process is tightly regulated and involves several key proteins. Initially, the cohesin complex keeps the chromatids attached to each other. When the cell is ready to separate the chromatids, separase becomes activated. Separase is an enzyme that cleaves cohesin, leading to the breakdown of the cohesion between the chromatids. Once cohesin is cleaved, the sister chromatids are no longer held together and are free to move toward opposite poles of the cell.
The protein securin regulates separase. Securin prevents separase from becoming active until the correct point in the cell cycle. When the cell is ready for anaphase, securin is targeted for degradation by the anaphase-promoting complex/cyclosome (APC/C), a crucial regulator of the cell cycle. Once securin is degraded, separase is activated, allowing the cleavage of cohesin and the separation of the sister chromatids.
Additionally, during mitosis, the kinetochore plays a role in attaching the chromatids to the spindle fibers. The spindle fibers, made of microtubules, pull the sister chromatids toward opposite poles of the cell during anaphase.
In summary, cohesin holds the sister chromatids together, separase cleaves cohesin to allow separation, and the spindle apparatus pulls the chromatids apart. The activation and regulation of these proteins ensure that the process of mitosis occurs accurately, with each daughter cell receiving the correct set of chromosomes.