Question

Choose the incorrect statement for the method homopolymer tailing.

(a) The first step is the RNA: DNA hybrid synthesis

(b) Terminal transferase is used for the addition of nucleotides on 3’ end

(c) Terminal transferase adds only at DNA strands

(d) The DNA strand is now having known sequence at 3’ end

I had been asked this question in an interview.

Origin of the question is cDNA Libraries, Polyadenylated RNA and cDNA Synthesis topic in section Libraries Construction of Genetic Engineering

Answer 1

Correct choice is (c) Terminal transferase adds only at DNA strands

Easy explanation: Homolpoymer tailing is also used for cDNA synthesis. The first step remains same as the other methods, which is the synthesis of RNA: DNA hybrid. It is then treated by terminal transferase, the enzyme is responsible for adding nucleotides on 3’ end of both DNA and RNA. The 3’ end is now having a known DNA sequence and it is used as a tail in the reaction.