Question
The chemical colchicine is used in the production of karyotypes. Colchicine prevents spindle fibers from forming during the cell cycle. What is a result of preventing spindle fibers from forming? A The cell cycle skips G_(0) phase and repeats G_(1) phase. B Mitotic division is skipped and the cell cycle proceeds to cytokinesis. Mitotic division stops in metaphase and cannot proceed to anaphase. The cell cycle skips S phase and proceeds to G_(2) phase.
Answer
4.1
(340 Votes)
Yale
Elite · Tutor for 8 years
Answer
C. Mitotic division stops in metaphase and cannot proceed to anaphase.
Explanation
Colchicine's role in cell division is pivotal, especially during the process of mitosis. Spindle fibers, essential for mitosis, are responsible for aligning and separating chromosomes. Colchicine disrupts the formation of spindle fibers. Understanding the phases of the cell cycle helps in analyzing the impact of inhibiting spindle fiber formation:1. **G0 Phase**: A resting stage where the cell is not actively preparing to divide.2. **G1 Phase**: The cell grows and prepares for DNA replication.3. **S Phase**: DNA replication occurs.4. **G2 Phase**: The cell prepares for mitosis.5. **Mitosis**: The cell divides its chromosomes into two sets in the nucleus, followed by division of the cell itself (cytokinesis).Without spindle fibers, chromosomes cannot be properly aligned and separated during mitosis. This specifically affects the transition from metaphase to anaphase in mitosis, as spindle fibers are crucial in this process. Metaphase is characterized by the alignment of chromosomes along the metaphase plate, a process facilitated by spindle fibers. Anaphase follows, where sister chromatids are pulled apart to opposite poles of the cell, a step that cannot occur without functional spindle fibers.Given this, the correct answer will be the one that reflects the interruption of mitosis at a stage where spindle fibers are essential. The other phases of the cell cycle (G0, G1, S, G2) are not directly affected by spindle fiber formation and thus are irrelevant in the context of colchicine's action.