The normal (wild-type) version of a particular protein includes a stretch of ami

Question

The normal (wild-type) version of a particular protein includes a stretch of amino acids as follows:

MET-TRP-VAL-ASP A mutant arose in this strain as a result of treatment with a mutagen known to change, delete or add single bases.

A new amino acid sequence of the mutant is now: MET-MET-GLY-STOP

Answer the following questions by referring to the attached genetic code.

a) Show the probable sequence(s) for mRNA which codes for this sequence of amino acids in the wild-type.

b) Show the new mRNA sequence in the mutant.

c) State specifically what mutational event the mutagen caused.

Explanation / Answer

Protein is formed from the mRNA through the process of translation.

1. Met - AUG,

Trp - UGG

Val - GUU, GUA, GUC, GUG

Asp - GAU, GAC

So the probable sequence of the mRNA would be

AUGUGGGUU(G,C,A)GAC(U)

B) The new mRNA sequence in the mutant would be

AUGAUGGGU(C,A,G)UAA/UAG/UGA

C) This is a nonsense mutation in which the mutation causes the protein to be shortened by replacing the bases in such manner that it results in shortening of the protein.

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