Shown below are the amino acid sequences of the wild-type and three mutant forms

Question

Shown below are the amino acid sequences of the wild-type and three mutant forms of a short protein.

What type of mutation does each represent (missense, nonsense etc)?

Specifically what change occurred in the mRNA sequence to result in the change in the amino acid sequence?

A fourth mutation in the gene is isolated. Analysis of the new mutation shows that the protein encoded has the wild-type sequence, but the amount of the protein produced is only about 10% of the normal amount. Where would you predict the mutation is located in this strain?

Wild type:     met-trp-tyr-arg-gly-ser-pro-thr

Mutant 1:     met-trp

Mutant 2:     met-trp-his-arg-gly-ser-pro-thr

Mutant 3:     met-cys-ile-val-val-val-gln-his

Explanation / Answer

The mutant 1 represent non sense mutation

Mutant 2 is mis sense mutation

Mutant three is mis sense mutation

2.in mutant 1 the mRNA codon is change to stop codon which lead to small chain formation where UAU/UAC is replaced by UAA/UAG.

In mutant 2 in this only one base pair is changed this type of mutation is pointmutation.In this transition substitution take placewhere pyrimidine is replaced by another pyrimidine (U by

C)which code fr another amino acid UAU/UACis replaced

byCAU/CAC.

In mutant 3 in this frame shift mutation take place where either

deletion or insertion of base pair change the complete reading frame.

3 .new mutant will show reduced amount of protein production due to incomplete or premature stoppage in protein production mutation will immediately occur near start codon which would lead to decrease in amount of protein production to 10%

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