State principle underlying 'gel electrophoresis' and mention two applications of this technique in biotechnology.

Explanation

**Step-by-Step Text 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 charged molecules through a gel matrix.

2. **Principle of Gel Electrophoresis:**
The principle underlying gel electrophoresis is that DNA molecules are negatively charged due to their phosphate backbone. When an electric current is applied, the DNA fragments migrate towards the positive electrode (anode). The movement of these fragments is influenced by their size; smaller fragments move faster and travel further through the gel, while larger fragments move more slowly and do not travel as far.

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