Question

A non-sense mutation has taken place in 49th codon of an mRNA coding a polypeptide of 100 aminoacid
How many amino acids will be incorporated in the new protein:

1) 2 separate polypeptide formed with 48 and 52 amino acids
2) Only one polypeptide formed with 100 aminoacid
3) Only one polypeptide formed with 48 aminoacid
4) Only one polypeptide formed with 52 aminoacid

Answer 1

Non sense mutation is a point mutation in which there is a change in codon in such a way that the new codon generated by mutation is stop codon , that is either of the following UAA , UAG , UGA.

Answer) Here non sense mutation has occurred at 49th codon , this will lead to change of 49th codon into stop codon. Therefore the new polypeptide will have only 48 amino acid.

As we are not given any further details we will assume that translation doesn't occurred after that

therefore answer is - option 3) Only one polypeptide formed with 48 amino acid