Animal cell division — timing of cleavage furrow formation In animal cells, the cleavage furrow that physically divides the cytoplasm forms during which specific part of cell division?

Introduction / Context:
Cytokinesis is the final act of cell division in animal cells, where the cytoplasm is partitioned to produce two distinct daughter cells. A hallmark of this process is the cleavage furrow driven by an actomyosin contractile ring.

Given Data / Assumptions:

• Mitosis (nuclear division) precedes cytokinesis (cytoplasmic division).
• Cleavage furrow formation is characteristic of animal cell cytokinesis.
• Furrow ingression is aligned roughly with anaphase/telophase transition and completes after chromosome segregation.

Concept / Approach:

The cleavage furrow forms during cytokinesis, often referred to here as the C phase. Signals from the anaphase spindle (central spindle and astral microtubules) position the contractile ring at the cell equator, where actin filaments and myosin II generate constrictive force, leading to abscission.

Step-by-Step Solution:

Verification / Alternative check:

Live-cell imaging shows furrow initiation shortly after sister chromatids separate, consistent with cytokinesis timing rather than G1, S, or G2.

Why Other Options Are Wrong:

G1, S, G2 are growth/replication phases without furrowing. ‘‘M phase’’ as a broad term includes cytokinesis in some textbooks, but the specific event ‘‘cleavage furrow’’ is properly assigned to cytokinesis (C phase).

Common Pitfalls:

Equating all of M phase with furrow formation; precise terminology differentiates nuclear division (mitosis) from cytoplasmic division (cytokinesis).

Final Answer:

C phase (cytokinesis)