Which of the following best describes siRNA?

• A. A short double-stranded RNA with one strand that can complimentarily bind to and inactivate an mRNA.
• B. A single-stranded RNA with internal complementary base pairs that allow it to fold into a cloverleaf pattern.
• C. A portion of rRNA which is a component of the large and small ribosomal subunits.
• D. A molecule, known as Dicer, that can degrade or cut RNA sequences.

Answer: (A)

Verified step by step guidance

1. Understand the role of siRNA (small interfering RNA) in the cell. It is involved in the RNA interference (RNAi) pathway, where it plays a role in gene silencing.
2. Recognize that siRNA is typically a short, double-stranded RNA molecule. This is a key characteristic that distinguishes it from other types of RNA.
3. Identify that one of the strands of siRNA can bind complementarily to a target mRNA. This binding is crucial for its function in silencing gene expression.
4. Note that the binding of siRNA to mRNA leads to the degradation of the mRNA, preventing it from being translated into a protein. This is how siRNA inactivates mRNA.
5. Compare the descriptions provided in the options to determine which one accurately describes siRNA. The correct description should highlight its double-stranded nature and its role in binding to and inactivating mRNA.