They bind to ribosomes. They bind to tRNA. They bind to RNA polymerase. They bind to mRNA.
I gave my students this multiple choice question: Cell differentiation is the result of gene expression. Genes can be regulated several ways. For example, small interference RNA molecules (siRNA), prevent gene expression by binding to the product of transcription. How do siRNA molecules silence genes?

Only one answer is correct among these 4 choices:
- They bind to ribosomes.
- They bind to tRNA.
- They bind to RNA polymerase.
- They bind to mRNA.

Could you tell me which one is correct?

They bind to mRNA.