An mRNA codon chart is shown below.
Suppose a DNA triplet has the sequence 3′-ATG-5′. Which of these three possible mutations of the triplet will stop translation?
3′-ACG-5′
3′-ATC-5′
3′-ATT-5′
The original DNA triplet "3′-ATG-5′" corresponds to the mRNA codon "AUG", which codes for the amino acid methionine and signals the start of translation.
If a mutation stops translation, it means that the codon will signal for the termination of the protein synthesis. The mRNA codons that signal for translation termination are known as stop codons.
Among the three mutations provided:
- 3′-ACG-5′ correspond to the mRNA codon "ACG", which codes for the amino acid Threonine
- 3′-ATC-5′ correspond to the mRNA codon "AUC", which codes for the amino acid Isoleucine
- 3′-ATT-5′ correspond to the mRNA codon "AUU", which codes for the amino acid Isoleucine
Therefore, none of the mutations provided will stop translation.