Electroforesis de ADN: Conceptos Básicos

Electrophoresis and Its Utility in Nucleic Acid Analysis

Introduction to Electrophoresis

• Electrophoresis is defined as the movement or dispersion of particles when subjected to an electric field, typically performed in a gel matrix.

• It is primarily used for separating molecules based on size, particularly DNA, which has negatively charged phosphate groups.

Mechanism of DNA Separation

• In agarose gel electrophoresis, the natural polysaccharide from algae is utilized to separate small DNA fragments up to kilobases; gels are usually run horizontally with running buffers like TAE or TBE.

• Polyacrylamide gel electrophoresis (PAGE) is mainly for protein separation but also effective for smaller nucleic acids due to its higher resolution.

Gel Formation and Sample Loading

• The formation of polyacrylamide gel involves polymerization initiated by ammonium persulfate and TEMED, creating a tighter polymer than agarose.

• Gels contain wells where samples are loaded; standards with known base pair sizes are often included for comparison.

Visualization Techniques

• After enzymatic digestion or genotyping assays, DNA bands can be visualized using ethidium bromide staining, which intercalates into DNA and fluoresces under UV light.

Advanced Electrophoresis Techniques

Pulsed Field Gel Electrophoresis (PFGE)

• PFGE is employed for larger DNA fragments (megabases); it changes voltage directionality to better resolve large chains.

• This method allows analysis of digested bacterial chromosomes, crucial in infectious disease research by examining restriction patterns.

Gradient Denaturing Electrophoresis

• This technique uses a urea and formamide gradient within the gel to denature DNA strands into single strands.

• The principle states that more denatured strands migrate less; migration patterns reveal mutations or unique genes based on their physical properties.

Capillary Electrophoresis