Anaphase I

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Definition

noun

The third stage in the first meiotic division after prophase I, and highlights the separation of paired homologous chromosomes towards opposite ends of the cell


Supplement

Meiosis is a specialized form of cell division that ultimately gives rise to non-identical sex cells. There are two successive nuclear divisions: meiosis I and meiosis II. Each of them has four major phases. These are prophase, metaphase, anaphase and telophase. Each of these phases is designated as I or II depending where it occurs, i.e. in meiosis I or in meiosis II.

Anaphase I is the third stage in meiosis I. It follows metaphase I, which highlights the movement of the paired homologous chromosomes towards the equatorial plane (called metaphase plate). They align themselves in such a way that the centromeres are directed towards the poles while the chromatids lie on the equatorial plane. The spindle fibers then attach to the kinetochores of the centromere joining the chromatids of the chromosome.

In anaphase I, the paired homologous chromosomes would separate from each other and move to opposite ends of the cell as the kinetochore microtubules shorten. This stage begins as soon as homologous chromosomes begin separating and ends when the chromosomes arrive at opposite ends of the cell. The next stage would be telophase I.

Meiotic anaphase I is different from mitotic anaphase in a way that the paired chromosomes are the ones that separate in anaphase I and not the sister chromatids (as in mitotic anaphase). Thus, the sister chromatids of each of a pair of homologous chromosomes would not separate yet at this stage.


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