RNAi Choose one: A. allows host cells to remember infection by copying small sections of viral DNA into RNA. B. occurs at random leading to the prevention of some key steps in the viral replication cycle. C. recognizes viral mRNA and prevents further viral gene expression. D. destroys the infected cells and halts viral production.

The correct answer is: C. recognizes viral mRNA and prevents further viral gene expression.

Explanation:

RNAi stands for RNA interference. RNAi can be defined as the process by which small RNA (Ribonucleic Acid) molecules of about 22 to 24 nucleotide length, which are produced from the host genome, are capable of binding to complementary RNA sequence present in the viral (RNA) genome or viral transcript resulting in the generation of double-stranded RNA molecules. These double stranded RNA molecules are recognised by RNase (ribonuclease) enzymes, which form the RISC or RNA-induced silencing complex, which is responsible for degrading the viral RNA thereby inhibiting viral gene expression. The small 22 to 24 nucleotide RNA molecules are synthesised by the host cell and are called the siRNAs or small interfering RNAs. Sometimes, these RNA molecules are synthesised in the form of a hairpin structure in the host. They are called the miRNAs or micro RNAs.