File:Kinetochore in mitosis and meiosis 01.jpg

Kinetochore attachment to the spindle and chromosome cohesion in mitosis and meiosis

Mitosis, mitotic chromosomes consist of two sister chromatids.

Kinetochore arrangement: one kinetochore faces one pole while its sister kinetochore faces the opposite pole and they move to opposite poles in anaphase. Chromosome cohesion: in metaphase, sister chromatids are held together by cohesion along chromosome arms and between centromeres. In anaphase both centromere and arm cohesion are released.

Meiosis I, Bivalents consist of two homologous chromosomes, each of which is composed of a pair of sister chromatids. Kinetochore arrangement: both sister kinetochores face the same spindle pole, while the homologous pair of sister kinetochores faces the opposite spindle pole. Therefore, in anaphase I, both sister chromatids of one homologue move toward the same pole. Chromosome cohesion: sister chromatids in meiosis I are held together by cohesion between centromeres and between arms of sister chromatids. The bivalent is held together by both recombination and arm cohesion. Recombination sites are at the junction between black and grey chromosome segments. In anaphase of meiosis I, arm cohesion is released and half-bivalents separate.

Meiosis II Each meiosis II chromosome consists of a pair of sister chromatids. Kinetochore arrangement: one kinetochore faces one pole, while its sister kinetochore faces the opposite pole. Consequently, sister kinetochores separate from one another in anaphase of meiosis II. Chromosome cohesion: in early stages of meiosis II, only the cohesion between centromeres remains; it is removed in anaphase II.

Reference

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