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.