Anaphase promoting complex (APC) is a protein degradation machinery necessary for proper mitosis of animal cells. If APC is defective in a human cell, which of the following is expected to occur

Options

A. Chromosomes will not condense
B. Chromosomes will be fragmented
C. Chromosomes will not segregate
D. Recombination of chromosome arms will occur

Answer

To solve the question regarding the effects of a defective Anaphase Promoting Complex (APC) in human cells during mitosis, we can break down the solution into clear steps:

### Step-by-Step Solution:

1. **Understanding the Role of APC**:
- The Anaphase Promoting Complex (APC) is crucial for the transition from metaphase to anaphase during mitosis. It facilitates the degradation of specific proteins that are necessary for the separation of chromosomes.

**Hint**: Remember that APC is involved in regulating the cell cycle, particularly during the transition between key phases of mitosis.

2. **Consequences of APC Defect**:
- If the APC is defective, the cell cannot properly transition from metaphase to anaphase. This means that the mechanisms that allow chromosomes to separate and move to opposite poles of the cell will fail.

**Hint**: Think about what happens during anaphase—chromosomes are pulled apart. What would happen if that mechanism is disrupted?

3. **Identifying the Effects on Chromosomes**:
- Because the APC is responsible for initiating the separation of chromosomes, a defect would lead to the chromosomes remaining aligned at the metaphase plate without moving to opposite ends of the cell.

**Hint**: Consider the phases of mitosis: what is the main event that occurs during anaphase?

4. **Eliminating Incorrect Options**:
- The question may provide multiple-choice answers. We can eliminate options that suggest:
- Chromosomes will condense (this occurs in prophase).
- Chromosomes will fragment (this is not a typical event in mitosis).
- Recombination of chromosome arms (this occurs during meiosis, not mitosis).

**Hint**: Focus on the definitions of the terms used in the options. Are they relevant to mitosis or meiosis?

5. **Conclusion**:
- The correct conclusion is that if APC is defective, the expected outcome is that **chromosomes will not segregate** properly during anaphase. This leads to potential problems such as aneuploidy (abnormal number of chromosomes) in the resulting daughter cells.

**Hint**: Reflect on the importance of proper chromosome segregation for genetic stability in cells.

### Final Answer:
If the Anaphase Promoting Complex (APC) is defective in a human cell, the expected outcome is that **chromosomes will not segregate** properly during mitosis.