Question

At the final step of First-strand cDNA Synthesis it has to be added RNase enzyme, Why?

Answer 1

At the final step of the first strand of cDNA synthesis, RNAse (especially RNAse H) is added to the mixture. RNase H does not degrade single and double-stranded DNA or unhybridized RNA. Instead it hydrolyses the RNA strand of a RNA-DNA hybrid.

In this mixture, this enzyme removes the mRNA bound to the cDNA after the first-strand cDNA synthesis. After mRNA is removed, primers can bind to the cDNA and synthesis of the second strand can begin. Thus the RNAse enzyme is crucial for complete cDNA synthesis.