Major factors that cause cancer are

Options

A. oncogenes and polymorphonuclear leucoytes
B. oncogenes and tumour suppressor genes
C. MHC genes
D. cellular oncogenes and `alpha`-interferons.

Explanation

**Step-by-Step Solution:**

1. **Understanding Cancer**:
- Cancer is defined as the uncontrolled growth of cells. This means that the normal regulatory mechanisms that control cell division and growth are disrupted, leading to excessive cell proliferation.

2. **Identifying Major Factors**:
- The major factors that contribute to the development of cancer include specific genes that play crucial roles in cell regulation. These are primarily oncogenes and tumor suppressor genes.

3. **Role of Oncogenes**:
- Oncogenes are genes that, when mutated or expressed at high levels, can lead to cancer. They are responsible for regulating cell proliferation, growth, and differentiation. Oncogenes promote cell division and can contribute to the transformation of normal cells into cancerous cells.

4. **Role of Tumor Suppressor Genes**:
- Tumor suppressor genes, on the other hand, function to inhibit cell division and keep mitosis in check. They play a critical role in preventing cancer by regulating the cell cycle and ensuring that cells do not divide uncontrollably. When these genes are mutated or lost, it can lead to unregulated cell growth and cancer development.

5. **Conclusion**:
- Based on the roles of oncogenes and tumor suppressor genes, the correct answer to the question regarding the major factors that cause cancer is **Option B: oncogenes and tumor suppressor genes**.

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