(A) G1
(B) G2
(C) S
(D) M
Colchicine disrupts microtubule formation, arresting cells during mitosis. This SEO article covers Q.51 with the correct answer and explanations for biology exam prep.
Correct Answer
The correct answer is (D) M.
Colchicine binds tubulin, preventing spindle fiber assembly needed for chromosome segregation in mitosis (M phase). This causes metaphase arrest, blocking progression to anaphase and often inducing polyploidy.
Option Breakdowns
(A) G1
G1 phase involves growth and preparation for DNA replication, without microtubule-dependent processes.
Colchicine targets mitotic spindles, not G1 activities like protein synthesis.
(B) G2
G2 phase checks DNA integrity post-replication, prior to mitosis entry.
Spindle formation occurs in prophase of M; colchicine acts later, not in G2.
(C) S
S phase duplicates DNA via semiconservative replication.
Colchicine does not interfere with DNA synthesis or replication forks.
(D) M
M phase (mitosis) requires microtubules for chromosome alignment and separation.
Colchicine depolymerizes tubulin, halting cells at metaphase.
| Option | Phase Activity | Colchicine Effect | Matches Q.51? |
|---|---|---|---|
| (A) G1 | Cell growth | None | No |
| (B) G2 | DNA damage check | None | No |
| (C) S | DNA replication | None | No |
| (D) M | Chromosome segregation | Spindle disruption | Yes |
