Question

The enzyme deoxynucleotdyl transferase adds poly G residues in the _________ in RT-PCR

• A. 3’ end of RNA
• B. 5’ end of RNA
• C. 3’ end of cDNA
• D. 5’ end of cDNA

Answer 1

Answer:

C. 3’ end of cDNA

• The enzyme terminal deoxynucleotidyl transferase (TdT) adds poly G residues to the 3' end of cDNA.

• This process is a specialized step, often used in Rapid Amplification of cDNA Ends (RACE), a variation of RT-PCR. In a typical RACE protocol, after a complementary DNA (cDNA) strand is synthesized from an mRNA template, TdT is used to add a homopolymer tail (like a string of guanine, or G, nucleotides) to the very end of the cDNA. This "tailing" step allows for the use of a complementary anchor primer during subsequent PCR amplification, enabling researchers to amplify and sequence the entire unknown 5' end of a gene.