OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What does the ribosome do during the translation stage of protein synthesis?

1. It synthesizes DNA

2. It reads the genetic code on mRNA

3. It breaks down proteins

4. It transports amino acids

The correct answer is: It reads the genetic code on mRNA

During the translation stage of protein synthesis, the ribosome plays a crucial role in interpreting the genetic code carried by messenger RNA (mRNA). The ribosome binds to the mRNA molecule and reads its sequence, which consists of codons—groups of three nucleotides that correspond to specific amino acids. As the ribosome moves along the mRNA, it facilitates the binding of transfer RNA (tRNA) molecules, each of which carries the appropriate amino acid. This process leads to the formation of a polypeptide chain, which eventually folds into a functional protein. The other options do not accurately reflect the ribosome's function during translation. Unlike the synthesis of DNA, which occurs during replication, translation specifically involves the assembly of proteins based on mRNA instructions. While some proteins may undergo breakdown through various cellular mechanisms, such as proteolysis, the ribosome does not perform this function. Additionally, while ribosomes do associate with tRNA, they do not transport amino acids themselves; rather, they assist in the assembly of amino acids into protein chains as instructed by the mRNA.