Recognition
of
the
Termination
Signal - Elongation of the polypeptide chain continues until a termination codon on mRNA is reached. The termination codon may be UAA (ochre), UAG (amber) or UGA (opal or umber). These codons have been called 'nonsense codons' because ordinarily no tRNA anticodons pair with them.
The termination codon need not be the last codon on mRNA. Polygenic mRNAs, which are common in bacteria and, bacteriophages, have a number of initiation and termination codons. Each segment of the mRNA between the initiation and termination codons directs the synthesis of a separate polypeptide chain
