Termination of translation is signalled by stop codons (UAG, UAA and UGA, in most organisms).
Translation is terminated by hydrolysis of the polypeptidyl-tRNA
linkage with concomittant release of mRNA and ribosomal subunits.
Stop codons are sufficient for termination. Yet, they can be made
more efficient by trans-acting factors.
Mutation of sense codons to nonsense codons (stop codons) results
in synthesis of a truncated polypeptide. In polycistronic mRNAs,
these mutations affect expression of downstream cistrons. The premature termination events can be suppressed by second-site mutations.
In eukaryotes, nonsense mutations can lead to destruction of the mRNA by a process called NMD.
