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

Question

The Anaphase Promoting Complex (APC) is crucial for the regulated degradation of proteins during mitosis in animal cells.  If a human cell has a defective APC, what is the most likely consequence?

B VENKAT · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
 **Primary Concept**: Cell cycle regulation and the role of the Anaphase-Promoting Complex (APC)
 **Related Topics**: Mitosis, cell cycle checkpoints, protein degradation, ubiquitin-proteasome system
 **Prerequisites**: Understanding of the stages of mitosis and the role of key regulatory proteins.
## SOLUTION PATHWAY
**Given Information**:
  Defective APC in a human cell.
  APC's role in regulated protein degradation during mitosis.
**Method & Steps**:
 1. Identify APC's function:
  Reasoning: The APC is a crucial enzyme complex that triggers the transition from metaphase to anaphase by marking specific proteins for degradation via the ubiquitin-proteasome system.  These proteins include securin and cyclin B.
  Formula/Rule: None directly applicable, but understanding the role of APC is key.
 2. Consider the consequence of a defective APC:
  Working: If the APC is defective, it cannot degrade these proteins.  This means that the proteins that prevent the separation of sister chromatids (e.g., securin) will remain bound, preventing the cell from progressing past metaphase.
  Key Point:  The cell cycle has checkpoints that ensure proper progression. A failure of the APC to degrade key proteins will halt progression at the metaphase checkpoint.
 3. Determine the most likely outcome:
  Result: Cell cycle arrest in metaphase.
  Verification: This is consistent with the known function of the APC and the consequences of its malfunction.
 ## OPTION ANALYSIS
A ✓: The cell cycle will arrest in metaphase. Correct, as the APC's inability to degrade securin and other proteins prevents the transition from metaphase to anaphase.
B :x: DNA replication occurs during the S phase, not directly related to APC function in mitosis.
C :x: A defective APC would likely *prevent* uncontrolled cell division, as it acts as a brake on the cell cycle.
D :x: G0 phase is a resting phase, a defective APC would not cause premature entry into this phase; it would cause arrest in a phase of the cell cycle.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the APC's role with other cell cycle regulators: Understanding the specific function of the APC is crucial.
  2.Assuming a defective APC would lead to uncontrolled cell division:  A defective APC actually leads to cell cycle arrest, preventing uncontrolled division.
 **Quick Tips**:
  1.Remember APC's role in metaphase-anaphase transition.
  2.Associate APC with the degradation of proteins that prevent sister chromatid separation.

B VENKAT · Answer

The correct Option is "The cell cycle will arrest in metaphase."

B VENKAT · Answer

DNA replication will not occur.

B VENKAT · Answer

The cell will undergo uncontrolled cell division.

B VENKAT · Answer

The cell will enter G0 phase prematurely.

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