Gel Electrophoresis

Overview

• Purpose: A technique for separating large molecules such as DNA fragments by size.
• Process: Uses an electric current to move molecules through a gel, allowing them to be identified and isolated.

Components

• Gel: Made from tangled polysaccharide polymer molecules in a saline solution.
  • Conducts electrical charge.
  • Small DNA fragments move further through the gel than large ones.
• Electrodes:
  • Negative electrode (top) where samples are loaded.
  • Positive electrode (bottom) to which DNA fragments are attracted.
• DNA Ladder:
  • Mixture of known DNA fragment sizes used for comparison.

Procedure

1. Setup:
   • Gel placed in a rectangular box with electrodes at each end.
   • Positive electrode at the far end from the sample wells.
2. Loading:
   • Samples added to wells in the gel near the negative electrode.
   • Saline solution covers gel and fills wells.
3. Separation:
   • Turn on electricity.
   • DNA fragments (negatively charged) move towards the positive electrode.
   • Smaller fragments travel farther than larger ones.

DNA Profiles

• Similarity and Variation: Key in distinguishing unrelated individuals.
• Forensic Use:
  • PR primers copy variable DNA fragments for unique profiles.
  • Multiple fragments reduce false matches.
  • Different countries use different numbers of fragments (e.g., USA uses 20).

Analysis

• Gel Photograph:
  • Shows many DNA bands.
  • Samples prepared with restriction enzymes and PCR primers.
  • Band positions indicate fragment size:
    • 10000 bases: minimal movement.
    • 100 bases (0.1 kilobases): move to the bottom.

Key Points

• Setup includes gel, electrodes, and saline solution.
• DNA moves from negative to positive electrode due to electrical current.
• Shorter fragments travel further in the gel.

Extension Idea

• Explore additional applications or advanced techniques related to gel electrophoresis.