Question 21

Electrophoresis is the most useful laboratory method to separate genomic DNA fragments by size.

Electrophoresis allows for the separation of DNA fragments based on their size, making it the most effective method for this purpose. This technique applies an electric field to a gel matrix, causing the DNA fragments to migrate at different rates, which enables their size differentiation.

A) Titration

Titration is a quantitative analytical method used to determine the concentration of a substance in a solution, typically through the addition of a reagent. It is not applicable for separating DNA fragments by size, as it does not involve any size-based separation techniques.

B) Spectrophotometry

Spectrophotometry measures the amount of light absorbed by a sample to determine its concentration or purity. While it can provide information about DNA concentration or quality, it does not separate DNA fragments by size, making it ineffective for this specific purpose.

C) Electrophoresis

Electrophoresis is the correct method for separating genomic DNA fragments by size. The technique utilizes an electric field applied to a gel, allowing smaller DNA fragments to move faster than larger ones, resulting in a size-based separation that is crucial for various molecular biology applications.

D) Filtration

Filtration is a method used to separate solids from liquids or gases using a porous material. It does not provide a mechanism for separating DNA fragments by size, as it is not designed for the resolution of molecular sizes, thus making it unsuitable for this laboratory task.

Conclusion

Electrophoresis is the definitive method for separating genomic DNA fragments by size, as it leverages the principles of size-dependent migration in an electric field. The other options fail to provide a suitable means for size separation, as they focus on different analytical or physical processes that do not apply to the separation of DNA fragments.