iGen3 07-04

Non-sense mutations in DNA

Written in the conventional way, theDNA template strand sequence 5'-CTT-3' DNA at left mutates to a 5'-CTA-3' at righ.t [HOMEWORK: what is the corresponding mutation in the DNA sense strand?]. The 5'-AAG'-3' mRNA codon therefore changes to a 5'-UAG-3' codon, and instead of adding a Lys (K) amino acid, the translation machinery introduces a release factor that terminate the protein prematurely. This is called a non-sense mutation, because the resulting codon has 'no sense', rather than having an incorrect or miss-sense for another amino acid.

Figure © 2010 PJ Russell, iGenetics 3rd ed.; all text material © 2012 by Steven M. Carr