Question

Choose the incorrect statement for the homopolymer tailing of cDNA strands.

(a) The blunt ended double stranded cDNA molecules are treated with terminal transferase and dCTPs

(b) Vector is also treated with terminal transferase and dGTPs

(c) The vector and cDNA can now anneal with the help of DNA ligase

(d) If gaps are created they can be repaired by physiological processes

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This is a very interesting question from Cloning the cDNA and Specialized Libraries topic in portion Libraries Construction of Genetic Engineering

Answer 1

Correct answer is (c) The vector and cDNA can now anneal with the help of DNA ligase

The explanation: For homopolymer tailing of cDNA strands, the blunt ended double stranded molecules are treated with terminal transferase and dCTPs. This leads to the addition of C residues at 3’ end. Vector is also treated with terminal transferase and dGTPs. This leads to annealing of vector and cDNA molecules and DNA ligase is not required. The gaps created can be repaired by physiological processes once the recombinant molecules enter the host.