Anafasen

Anafasen, commonly referred to as anaphase in many languages, is a stage of cell division during which genetic material is segregated and moved toward opposite poles. It occurs in both mitosis and meiosis, following metaphase and preceding telophase and cytokinesis.

In mitosis, the centromeres split and the sister chromatids are pulled apart. This separation is driven by shortening of kinetochore microtubules as they depolymerize and by motor proteins that move along microtubules. The cohesin proteins that hold sister chromatids together are cleaved by the protease separase, activated after the anaphase-promoting complex/cyclosome (APC/C) targets securin for degradation. As chromatids separate, non-kinetochore microtubules lengthen, contributing to elongation of the cell and further poleward movement of the chromosomes.

In meiosis, the term encompasses two distinct transitions: anaphase I, where homologous chromosomes are pulled to opposite poles, and anaphase II, where sister chromatids separate. In both cases, spindle dynamics and regulated proteolysis ensure accurate chromosome segregation.

Regulation of ana-fase is tightly controlled by the spindle assembly checkpoint, which ensures chromosomes are properly attached to the spindle before progression. Key players include APC/C, securin, separase, and cyclin-dependent kinases. Disruptions in this phase can lead to aneuploidy, a common feature of certain cancers and genetic disorders. The concept and mechanics of anafasen reflect fundamental principles of chromosome behavior during cell division across eukaryotes.