Anaphase

Anaphase

Anaphase IF

Stages of late M phase in a vertebrate cell

Anaphase is a critical phase within cell division, specifically during mitosis and meiosis, where replicated chromosomes are split and moved to opposite ends of the cell. This process ensures that each daughter cell receives an identical set of chromosomes, thus maintaining genetic continuity through cellular generations. Anaphase is preceded by metaphase and followed by telophase.

Overview

During anaphase, the cohesin proteins that hold the sister chromatids together are cleaved, allowing them to separate. This separation is facilitated by the mitotic spindle, a structure composed of microtubules and associated proteins, which pulls the chromatids apart with the help of motor proteins. Anaphase can be subdivided into two distinct stages: Anaphase A and Anaphase B.

Anaphase A

In Anaphase A, the chromatids, now referred to as daughter chromosomes, are pulled toward the spindle poles. This movement is primarily driven by the shortening of the kinetochore microtubules, which attach to the kinetochore region on the chromosomes.

Anaphase B

Anaphase B involves the elongation of the cell itself, through the polar microtubules pushing against each other, which helps in separating the two sets of chromosomes further apart. Additionally, the spindle apparatus reorganizes itself to prepare for the completion of cell division.

Significance

The accurate segregation of chromosomes during anaphase is crucial for genetic stability. Errors in chromosome separation can lead to aneuploidy, a condition where cells have an abnormal number of chromosomes, which is associated with various diseases, including cancer and Down syndrome.

Regulation

The transition from metaphase to anaphase is tightly regulated by several protein complexes, including the Anaphase-Promoting Complex (APC/C), which targets securin, an inhibitor of separase, for degradation. Once securin is degraded, separase is activated, which then cleaves the cohesin proteins, allowing the sister chromatids to separate.

In Meiosis

Anaphase in meiosis occurs twice, once in Meiosis I and again in Meiosis II, with slight differences in each. In Meiosis I, it is the homologous chromosomes that are separated, reducing the chromosome number by half. In Meiosis II, similar to mitosis, the sister chromatids are separated.

See Also

• Cell division
• Mitosis
• Meiosis
• Chromosome
• Cytokinesis