Question

How can gradient in the field strength be obtained?

(a) It can be obtained via varying the amount of current, keeping the resistance constant

(b) It can be obtained via varying the amount of resistance, keeping the current constant

(c) Both can be varied, but resistance is having more effect

(d) Buffer-gradient gels can be used with decreasing concentration of buffer at the bottom

This question was posed to me in examination.

My query is from Gel Electrophoresis, Oligonucleotide  & Microarrays in chapter Basics of Genetic Engineering of Genetic Engineering

Answer 1

The correct option is (b) It can be obtained via varying the amount of resistance, keeping the current constant

Explanation: The gradient field strength can be obtained via varying the resistance because the current flowing throughout the gel needs to remain constant. To vary the resistance, often buffer-gradient gels and wedge gels can be used. Wedge gels are thick and thus are having lower resistance at the bottom. Whereas buffer-gradient gels with increasing concentration at the bottom are used. As the concentration increases at the bottom, resistance decreases.