Anaphase

Definition

Anaphase is a stage in the process of mitosis where the replicated chromosomes are pulled apart and moved toward opposite poles of the cell. This stage is crucial as it ensures that each daughter cell receives an identical set of chromosomes, maintaining genetic consistency. During anaphase, the sister chromatids separate due to the action of spindle fibers, which are formed during earlier phases of mitosis, and this event is tightly regulated to prevent errors in chromosome distribution.

5 Must Know Facts For Your Next Test

1. During anaphase, the separation of sister chromatids is triggered by the enzyme separase, which cleaves the cohesin protein holding them together.
2. Anaphase can be divided into two sub-stages: anaphase A, where the chromatids are pulled apart, and anaphase B, where the poles of the cell move further apart.
3. The movement of chromatids during anaphase relies on the shortening of microtubules attached to kinetochores, which are protein structures on the centromere.
4. Errors during anaphase can lead to aneuploidy, a condition where cells have an abnormal number of chromosomes, often resulting in serious genetic disorders.
5. Anaphase is followed immediately by telophase, where chromosomes begin to de-condense and nuclear envelopes reform around each set of chromosomes.

Review Questions

• How does anaphase ensure accurate chromosome distribution during cell division?
  • Anaphase plays a critical role in ensuring accurate chromosome distribution by separating sister chromatids and pulling them toward opposite ends of the cell. This separation is facilitated by spindle fibers that attach to kinetochores on each chromatid, ensuring that each daughter cell receives one copy of every chromosome. The precise regulation of this process is vital for maintaining genetic stability and preventing conditions such as aneuploidy.
• Discuss the role of the spindle apparatus in the mechanics of anaphase.
  • The spindle apparatus is essential for the mechanics of anaphase as it consists of microtubules that anchor to kinetochores and help separate sister chromatids. During anaphase A, these microtubules shorten, pulling chromatids toward opposite poles. In anaphase B, other microtubules push against each other, causing the spindle poles to move further apart. This coordinated movement ensures that chromosomes are evenly distributed between daughter cells.
• Evaluate the implications of errors occurring during anaphase on cellular function and organismal health.
  • Errors during anaphase can lead to aneuploidy, resulting in cells with missing or extra chromosomes. This can disrupt normal cellular function and lead to diseases such as cancer, where abnormal chromosome numbers can promote uncontrolled cell growth. Additionally, conditions like Down syndrome result from specific chromosomal abnormalities due to improper segregation during anaphase. Therefore, understanding anaphase and its regulation is crucial for insights into developmental biology and disease mechanisms.

Related terms

Chromatid: A chromatid is one half of a duplicated chromosome, which is joined to its identical sister chromatid by a centromere.

Spindle Apparatus: The spindle apparatus is a structure made of microtubules that orchestrates the movement of chromosomes during cell division.

Cytokinesis: Cytokinesis is the process that follows mitosis, dividing the cytoplasm of a parent cell into two daughter cells.