Which type of RNA is primarily responsible for assembling proteins at the ribosome?

• A. mRNA
• B. tRNA
• C. rRNA
• D. snRNA

Answer: (C)

Ribosomal RNA provides the core structure of the ribosome and acts as its catalytic center during protein synthesis. The ribosome is made of rRNA and proteins, and the rRNA within it actually catalyzes peptide bond formation between amino acids as the new protein is built. Messenger RNA carries the genetic code that tells the ribosome which amino acids to add, but it does not perform the chemistry of linking them. Transfer RNA brings the correct amino acids to the ribosome and matches them to the mRNA codons, yet it is the rRNA that drives the chemistry of assembly. Small nuclear RNA is involved in splicing pre-mRNA in the nucleus, not in assembling proteins at the ribosome. Therefore, the RNA primarily responsible for assembling proteins at the ribosome is ribosomal RNA.