Question

Examine the DNA triplets here and determine the amino acid sequence they code for. Then provide a different DNA sequence that will produce the same protein. TAC CAG ATA CAC TCC CCT, then create the following: (i) frameshift mutation; (ii) a silent mutation; and (iii) a nonsense mutation. thanks

Answer 1

TAC CAG ATA CAC TCC CCT       DNA sequence

AUG GUC UAU GUG AGG GGU   mRNA sequence

Met-Val-Tyr-Val-Arg-Gly               Polypeptide Sequence

Met-Val-Tyr-Val-Arg-Gly               Polypeptide Sequence

AUG GUU UAC GUA AGA GGU   mRNA sequence

TAC CAA ATG CAT TCT CCA   DNA Sequence

This is due to redundant nature of genetic code, i.e., most of the amino acids are encoded by more than one codons.

1) Frameshift Mutation (Deletion/Insertion).

Deletion of A at 9th position, leads to premature termination of translation at 3rd codon.

TAC CAG ATC ACT CCC CT       DNA sequence

AUG GUC UAG UGA GGG GU   mRNA sequence

Met-Val-STOP                              Polypeptide Sequence

2) Silent mutation (Change via substitution in the DNA sequence without affecting the polypeptide sequence).

Replacing C at 12th position by T would affect DNA sequence but not the protein sequence as both GUG and GUA codes for Valine.

TAC CAG ATA CAT TCC CCT       DNA sequence

AUG GUC UAU GUA AGG GGU   mRNA sequence

Met-Val-Tyr-Val-Arg-Gly               Polypeptide Sequence

3) Nonsense Mutation (Deletion or insertion leading to premature termination of translation).

Deletion of A at 9th position, leads to premature termination of translation at 3rd codon.

TAC CAG ATC ACT CCC CT       DNA sequence

AUG GUC UAG UGA GGG GU   mRNA sequence

Met-Val-STOP                              Polypeptide Sequence.