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) and 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-tyr

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

Mutant 3:      met-trp-his-arg-gly-ser-pro-thr

Explanation / Answer

Mutant 1-deletion mutation as the amino acids get deleted..

Mutant 2- it can be due to inversion mutation whre the same amount of gene is inverted hence coding for different amino acids. Which can be peri centric and paracentric

Mutant 3- missense mutation as due to substitution point mutation in one nucleotide results in coding of different amino acids ie histadine in place of tyrosine..

The fourth Mutant may be affected at the Promoter site or the enhancer site as it control the rate of the transcription and as well as translation by increasing its effectiveness. But as they are mutated it leads to depression of gene expression.

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