The Question is from neet-botany cell-cycle-and-cell-division , and it was created by the author B VENKAT

Question

In an experiment, cells are arrested in metaphase using colchicine, a drug that inhibits microtubule polymerization. If these cells are then fused with cells in G1 phase, what is the most likely outcome for the G1 chromosomes?

B VENKAT · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: Cell cycle control and chromosome behavior
 **Related Topics**: Mitosis, cell fusion, microtubules, colchicine
 **Prerequisites**: Understanding of the cell cycle phases (G1, metaphase), the role of microtubules in mitosis, and the effect of colchicine.
## SOLUTION PATHWAY
**Given Information**:
  * Cells arrested in metaphase (condensed chromosomes) using colchicine (inhibits microtubule polymerization).
  * Fusion with G1 phase cells (chromosomes in uncondensed state).
  * Colchicine prevents the formation of the mitotic spindle, essential for chromosome segregation in mitosis.
**Method & Steps**:
 1. Metaphase cells have already replicated their DNA and their chromosomes are highly condensed.
  Reasoning: Colchicine arrests cells in metaphase by preventing microtubule polymerization, a critical step for chromosome separation.  The chromosomes are already condensed in metaphase.
  Formula/Rule: N/A
 2. When fused with G1 phase cells, the factors present in the metaphase cytoplasm (cytoplasmic factors responsible for chromosome condensation) will influence the G1 chromosomes.
  Working: The metaphase-promoting factor (MPF), which drives chromosome condensation, is highly active in metaphase cells.  Upon fusion, this factor can diffuse into the G1 cell. 
  Key Point: The cytoplasm of the metaphase cell contains regulatory proteins that control chromosome condensation.
 3. The G1 chromosomes, under the influence of these cytoplasmic factors, will condense prematurely, mimicking the condensation seen in metaphase.
  Result: Premature chromosome condensation in the G1 cells.
  Verification:  This is consistent with the experimental observation that cytoplasmic factors from mitotic cells can induce premature chromosome condensation in interphase nuclei.
 ## OPTION ANALYSIS
A :x: The G1 chromosomes have not yet replicated their DNA; this process occurs in the S phase.
B ✓: The G1 chromosomes will condense prematurely due to the influence of cytoplasmic factors from the metaphase cell.
C :x: The G1 chromosomes are directly affected by the factors in the metaphase cytoplasm. 
D :x: Colchicine inhibits microtubule polymerization, which is involved in chromosome segregation, not fragmentation.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the effects of colchicine on microtubule polymerization with its effect on DNA replication: Colchicine does not directly affect DNA replication.
  2.Assuming that only nuclear factors control chromosome condensation: Cytoplasmic factors play a significant role.
 **Quick Tips**:
  1.Remember that metaphase cells have already replicated their DNA and condensed their chromosomes.
  2.Cytoplasmic factors from mitotic cells can induce premature chromosome condensation.

B VENKAT · Answer

The G1 chromosomes will replicate their DNA.

B VENKAT · Answer

The correct Option is "The G1 chromosomes will condense prematurely."

B VENKAT · Answer

The G1 chromosomes will remain unaffected.

B VENKAT · Answer

The G1 chromosomes will fragment.

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