Gene therapy involves

Options

A. introduction of a normal genes in cell
B. treating of defective genes with radiation
C. eliminating defective and useless genes
D. replacement of defective genes by normal

Answer

**Step-by-Step Solution:**

1. **Understanding Gene Therapy**: Gene therapy is a medical technique that aims to treat or prevent diseases by modifying the genes within an individual's cells. It primarily focuses on correcting defective genes responsible for disease development.

2. **Analyzing the Options**:
- **Option 1**: "Introduction of a normal gene in a cell" - While this sounds relevant, gene therapy specifically involves replacing defective genes rather than just introducing normal genes without addressing the defect.
- **Option 2**: "Treating of defective genes with radiation" - This is not a method of gene therapy; radiation is more associated with cancer treatment and not gene correction.
- **Option 3**: "Eliminating defective and useless genes" - This option is misleading as it suggests that some genes are useless, which is not accurate. All genes have a role, and eliminating them is not a method used in gene therapy.
- **Option 4**: "Replacement of defective genes by a normal gene" - This accurately describes gene therapy, where the goal is to replace or repair defective genes to restore normal function.

3. **Conclusion**: After analyzing all the options, the most accurate description of gene therapy is found in **Option 4**, which states that it involves the replacement of defective genes by a normal gene.

**Final Answer**: Option 4 - Replacement of defective genes by a normal gene.

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