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 the probable mRNA sequence of these amino acid will be

the mRNA sequence in the wild type protein is AUG-UGG-GUG-GAU as these codon codes for methione ,tryptophan valine and asparagine.

the new sequence in the mutant is AUG-AUG-GGG-UAG which codes for methione ,methione glycine and stop codon.

the mutational event is point mutation where addition and deletion of a base cause in the change of amino acid.

change from trptophan to methione in mutant type occurs when uracil changes to adenosine at first position and guanine changes to uracil at second position (i.e. U to Aand G to u). this is called missense mutation.

in valine to glycine the GUG sequence change to GGG (as Guanine in 2 Place changes to uracil.

similarly in mutant type no protein is synthesised as it is example of nonsense point mutation whereGAU changes to UAG.

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