Question

Choose the correct statement for RNA fractionation.

(a) The RNA is fractioned by size but before separating on oligo-dT cellulose

(b) A sucrose density gradient is used

(c) The RNA is applied to the top of a pre-poured gradient and during centrifugation smaller molecules move down the tube faster

(d) Different bands are formed according to the density in the sucrose density gradient

This question was posed to me in an interview.

The origin of the question is Cloning the cDNA and Specialized Libraries topic in chapter Libraries Construction of Genetic Engineering

Answer 1

Correct choice is (b) A sucrose density gradient is used

The best I can explain: RNA fractionation is carried out and the basis is the size. It is fractioned by size after carrying out separation on oligo-dT cellulose. A sucrose density is used for size based separation. The RNA is applied to the top of a pre-poured gradient and during centrifugation larger molecules move down the tube faster. There are different bands formed on the basis of size in the sucrose density gradient.