sister chromatids attach to each other in nearby relationship.
sister chromatids attach to each other in nearby relationship.
where do sister chromatids attach to each other?
nearby relationship
the bfb cycle begins when the end region of a chromosome, called its telomere, breaks off. when that chromosome subsequently replicates it forms two sister chromatids which both lack a telomere. since telomeres appear at the end of chromatids, and function to prevent their ends from fusing with other chromatids, the lack of a telomere on these two sister chromatids causes them to fuse with one another. during anaphase the sister chromatids will form a bridge where the centromere in one of the sister chromatids will be pulled in one direction of the dividing cell, while the centromere of the other will be pulled in the opposite direction. 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. this results in the two daughter cells receiving an uneven chromatid. since the two resulting chromatids lack telomeres, when they replicate the bfb cycle will repeat, and will continue every subsequent cell division until those chromatids receive a telomere, usually from a different chromatid through the process of translocation.
breakage-fusion-bridge cycle
in "s. cerevisiae", esp1 is coded by esp1 and is regulated by the securin pds1. the two sister chromatids are initially bound together by the cohesin complex until the beginning of anaphase, at which point the mitotic spindle pulls the two sister chromatids apart, leaving each of the two daughter cells with an equivalent number of sister chromatids. the proteins that bind the two sister chromatids, disallowing any premature sister chromatid separation, are a part of the cohesin protein family. one of these cohesin proteins crucial for sister chromatid cohesion is scc1. esp1 is a separase protein that cleaves the cohesin subunit scc1 (rad21), allowing sister chromatids to separate at the onset of anaphase during mitosis.
separase