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

a)Probable sequences of mRNA of wild types are as AUG code for Methionine, UUG codes for Tryptophan, GUU, GUC, GUA, GUG valine and GAU and GAC codes for aspartic acid

AUG-UGG-GUU- GAU

AUG-UGG- GUC- GAU

AUG-UGG- GUA- GAU

AUG-UGG- GUG- GAU

AUG-UGG-GUU- GAC

AUG-UGG- GUC- GAC

AUG-UGG- GUA- GAC

AUG-UGG- GUG- GAC

b)The sequence in tne mRNA of muatant is

AUG-AUG-GGU-UAG

where UAG codes for stop codons and GGU codes for glycine and AUG codes for Methionine

C) The mutation occured might be substitution mutation exchanges one base for another such as switching an A to G. change an amino-acid-coding codon to a single "stop" codon and cause an incomplete protein.

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