Gene therapy has been successful in curing genetic diseases in laboratory animals through

Options

A. exposure to X-ray to rectify the defective gene
B. replacing the defective gene with a functional gene
C. oral delivery of genes
D. use of therapeutic medicines to rectfy the Defective genes

Answer

### Step-by-Step Solution:

1. **Understanding Gene Therapy**: Gene therapy is a technique that involves the introduction, removal, or alteration of genetic material within a person's cells to treat or prevent disease. The primary goal is to correct defective genes responsible for disease development.

2. **Identifying the Options**: The question provides four options regarding how gene therapy has been successful in curing genetic diseases in laboratory animals:
- A) Exposure to x-ray to rectify the defective gene
- B) Replacing the defective gene with a functional gene
- C) Oral delivery of the gene
- D) Use of therapeutic medicines to rectify the defective gene

3. **Evaluating Each Option**:
- **Option A**: Exposure to x-ray is not a method used in gene therapy. X-rays are typically used in radiation therapy for cancer treatment, not for gene correction.
- **Option B**: Replacing the defective gene with a functional gene is a core principle of gene therapy. This approach aims to provide the cells with a normal copy of the gene, thus restoring normal function.
- **Option C**: Oral delivery of the gene is not a standard method in gene therapy. Gene delivery usually requires more direct methods, such as viral vectors or other delivery systems.
- **Option D**: While therapeutic medicines can help manage symptoms, they do not directly rectify defective genes like gene therapy does.

4. **Conclusion**: The most accurate and relevant option in the context of gene therapy is **Option B**: replacing the defective gene with a functional gene. This method has been shown to be effective in laboratory settings for curing genetic diseases.

### Final Answer:
Gene therapy has been successful in curing genetic diseases in laboratory animals through **replacing the defective gene with a functional gene**.

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