When ribosomes encounter broken or incomplete mRNAs, what do they do?

When ribosomes encounter broken or incomplete mRNAs, they typically stall and do not release. This stalling occurs because the ribosome is unable to translate an incomplete transcript, which could lead to divergent polypeptide chains or the production of non-functional proteins. This could result from lacking essential reading frame information found in complete mRNAs.

The stalling of the ribosome signals a problem with the mRNA, preventing any further translation from occurring. This process allows for quality control within the cell, making sure that only properly formed and complete mRNAs are translated into proteins. Stalled ribosomes can then trigger cellular mechanisms that remove defective mRNA molecules, ensuring that these unproductive transcripts do not accumulate and interfere with normal cellular function.