Question

Which technique is used to separate nucleic acids of size greater than 25 kb?

(a) SDS-PAGE

(b) Pulsed-field electrophoresis

(c) 2D- gel electrophoresis

(d) Isoelectric focusing

I have been asked this question in an online quiz.

The question is from Nucleic-acid Techniques in portion Techniques in Cell Biology of Cell Biology

Answer 1

The technique used to separate large nucleic acids, particularly those with sizes greater than 25 kb, is pulsed-field electrophoresis. This method is a modification of gel electrophoresis that applies an alternating electric field, allowing very large DNA fragments to navigate the gel more effectively and separate based on size.

Let’s review each option:

• (a) SDS-PAGE: This technique is mainly used for separating proteins based on their molecular weight and is not suitable for large nucleic acids.

• (b) Pulsed-field electrophoresis: Correct. Pulsed-field electrophoresis is specifically designed to separate large DNA molecules (up to several megabases), making it ideal for nucleic acids over 25 kb.

• (c) 2D-gel electrophoresis: This technique is generally used for proteins, providing separation in two dimensions but is not suitable for large nucleic acids.

• (d) Isoelectric focusing: This technique separates molecules based on their isoelectric points, mainly used for proteins and not for large nucleic acids.

Correct Answer: (b) Pulsed-field electrophoresis