Nonsense-mediated MRNA Decay
Despite an expected tendency for premature termination codons to yield shortened polypeptide products, in fact the formation of truncated proteins does not occur often in vivo. Many organisms—including humans and lower species, such as yeast—employ a nonsense-mediated mRNA decay pathway, which degrades mRNAs containing nonsense mutations before they are translated into nonfunctional polypeptides.
Read more about this topic: Nonsense Mutation