Which of the Following Scenarios Is the Most Likely Mechanism

Multiple Choice

Which of the following scenarios is the most likely mechanism by which RNAi silences the expression of genes?

A) RNAi binds to a mRNA strand before it reaches the ribosome, thereby preventing translation.
B) RNAi binds to mRNA strand after it leaves the ribosome which prevents translation.
C) RNAi binds to DNA which prevents transcription.
D) RNAi binds to RNA primase which prevents the transcription of the gene.
E) RNAi binds to helicase which prevents DNA replication and thereby the expression of the gene.