Question

Colchicine results in doubling of chromosome number because of

• A. Non-formation of spindle
• B. Double replication of chromosomes
• C. Non-pairing of chromosomes
• D. Splitting of chromatids

Answer 1

Answer: (D)

Splitting of chromatids

Colchicine, an anti-mitotic substance, inhibits microtubule polymerization by binding to tubulin, which is a main constituent of microtubules. Microtubules play a role in the migration of chromosomes to opposite ends of a mitosing cell during the anaphase. In anaphase, chromatids separate and move to opposite poles by spindle fibers. This allows each daughter cell to have an identical copy of each of the original cell’s chromosomes. Therefore, availability of tubulin is necessary for this phase of mitosis. Colchicine does not allow separation of chromatids. Hence, it effectively functions as a "mitotic poison" or spindle poison. Colchicine does not inhibit chromosome replication.