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 50% higher than the normal amount. Where would you predict the mutation is located in this strain?

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

Mutant 1:     met-trp-cys-arg-gly-lys-pro-thr

Mutant 2:     met-trp-tyr-arg-arg-gln-ala-asp

Mutant 3:     met-trp-tyr-arg

Explanation / Answer

Mutant 1- it is due to the substitution mutation whre one nucleotide is substituted or replaced resulting in the change of reading frame and change of amino acid sequence

Mutant 2 - it is a miss sense mutation which may happens due to the insertion mutation whre one nucleotide is added or inserted in the wild type which result in the change of codon reading frame hence same length of amino acids are formed.

Mutant 3 - it the non - sense mutation whre there is a insertion of a stop codon which result in the sudden stop of protein synthesis hence the length of the amino acids decreases which may result in truncated protein.

Mutant 4- in this strain 50% may be due to the following reasons.

(a) - the mutation may occur in the Promoter Site Which Will Result In The Strong Binding Of The Translation Factors Resuting In High Expression.

(b) The Mutation May Occurs In The RNA itself Which Is Associated In The Formation Of Hair-pin Loop in Promoter Region ThUs Inhibiting Translation. Hence Those RNA sequence Might Have Change Resulting In No Hair-pin Loop Hence Incresead Translation

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