The anaphase-promoting complex is activated by

Options

A. M cdk cyclin
B. G 1 cdk cyclin
C. S cdk cyclin
D. Transcription factor

Answer

To determine what activates the anaphase-promoting complex (APC), we can analyze the options provided in the question step by step.

### Step-by-Step Solution:

1. **Understanding the Anaphase-Promoting Complex (APC)**:
- The APC is a crucial protein complex that plays a significant role in regulating the cell cycle, specifically during the transition from metaphase to anaphase.

2. **Evaluating the Options**:
- **Option 1: MCDK Cyclin**:
- MCDK (M-phase Cyclin-dependent Kinase) is involved in the regulation of the cell cycle during the M phase, particularly in promoting the transition from metaphase to anaphase. It activates the APC, which leads to the degradation of proteins that inhibit anaphase, allowing chromosome separation.
- **Option 2: G1 CDK Cyclin**:
- G1 CDK Cyclin is involved in the G1 phase of the cell cycle, promoting the cell's progression into the S phase. It does not directly activate the APC.
- **Option 3: SCDK Cyclin**:
- SCDK Cyclin is primarily active during the S phase, promoting DNA replication. It does not play a role in activating the APC.
- **Option 4: Transcription Factor**:
- Transcription factors are involved in regulating gene expression and do not directly activate the APC.

3. **Conclusion**:
- Based on the analysis, the correct answer is **MCDK Cyclin**, as it is specifically responsible for activating the anaphase-promoting complex during the cell cycle.

### Final Answer:
The anaphase-promoting complex is activated by **MCDK Cyclin**.