Cancer is caused by all of the following except

Options

A. Cellular oncogenes
B. Tumour suppressor gene
C. Viral oncogens
D. Chemical carcinogens

Answer

To solve the question "Cancer is caused by all of the following except," we need to analyze each of the options provided and determine which one does not contribute to the development of cancer.

### Step-by-Step Solution:

1. **Identify the Options**: The options given are:
- Cellular oncogenes
- Tumor suppressor genes
- Viral oncogenes
- Chemical carcinogens

2. **Analyze Cellular Oncogenes**:
- Cellular oncogenes are genes that can transform a normal cell into a cancerous cell when mutated or expressed at high levels.
- Example: HER2 is a well-known oncogene associated with certain types of cancer.
- **Conclusion**: Cellular oncogenes contribute to cancer.

3. **Analyze Viral Oncogenes**:
- Viral oncogenes are genes from viruses that can lead to cancer.
- Examples include the Hepatitis B Virus (HBV), Human Papillomavirus (HPV), and Human Herpesvirus 8.
- **Conclusion**: Viral oncogenes also contribute to cancer.

4. **Analyze Chemical Carcinogens**:
- Chemical carcinogens are substances that can lead to cancer through chemical exposure.
- Examples include asbestos, radon, vinyl chloride, and benzene.
- **Conclusion**: Chemical carcinogens are known to cause cancer.

5. **Analyze Tumor Suppressor Genes**:
- Tumor suppressor genes are responsible for regulating cell division and preventing uncontrolled cell growth.
- Examples include BRCA1 and BRCA2, which help prevent cancer.
- **Conclusion**: Tumor suppressor genes do not cause cancer; instead, they help prevent it.

6. **Identify the Exception**:
- Since cellular oncogenes, viral oncogenes, and chemical carcinogens all contribute to cancer, the only option that does not cause cancer is the tumor suppressor genes.

### Final Answer:
**Tumor suppressor genes** are the exception; they do not cause cancer.

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