Gel electrophoresis is used for

Options

A. construction of r-DNA
B. isolation of DNA
C. cutting of DNA
D. separation of DNA fragments according to their size or length

Answer

**Step-by-Step Solution:**

1. **Understanding Gel Electrophoresis**: Gel electrophoresis is a laboratory technique used to separate DNA fragments based on their size. It utilizes an electric field to move the negatively charged DNA through a gel matrix.

2. **Components of Gel Electrophoresis**:
- **Gel Medium**: The gel used is typically agarose, which acts as a sieve to separate DNA fragments.
- **Apparatus**: The setup consists of a rectangular chamber where the gel is poured, and electrodes are placed at both ends to create an electric field.

3. **Process of Gel Electrophoresis**:
- **Preparation**: DNA samples are mixed with a loading dye and loaded into wells in the agarose gel.
- **Application of Electric Field**: When the electric field is applied, DNA fragments move towards the positive electrode due to their negative charge.
- **Separation**: Smaller DNA fragments move faster and travel further through the gel than larger fragments, resulting in separation based on size.

4. **Visualization**: After the electrophoresis is complete, the DNA fragments can be stained with a specific dye (like ethidium bromide) to visualize them under UV light.

5. **Conclusion**: Gel electrophoresis is primarily used for the separation of DNA fragments according to their size.

**Final Answer**: Gel electrophoresis is used for the separation of DNA fragments according to their size.

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