Shown below are protein. the amino acid sequences of the wild-type and three mut
ID: 265655 • Letter: S
Question
Shown below are protein. the amino acid sequences of the wild-type and three mutant forms of a short a. What type of mutation does each represent (missense , nonsense ete)? b. Specificall y what change occurred in the mRNA sequence to result in the change in the amino acid sequence? c. A fourth mutation in the gene is isolated. Analysis of the new mutation shows that the protein encoded has the wild-type sequence, but cells produce 50% more protein than in wildtype cells. 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-ty Mutant 2: met-trp-tyr-arg-ala-leu-ala-gln Mutant 3: met-trp-his-arg-gly-ser-pro-thr Shown below are the amino acid sequences of the wild-type and three mutant forms of a short protein. a. What type of mutation does each represent (missense, nonsense etc)? b. Specifically what change occurred in the mRNA sequence to result in the change in the amino acid sequence? c. 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 Be sure you are familiar with the different types of vectors used in molecular genetics, and what each type is most commonly used for.Explanation / Answer
First Part:
a) Missense mutation: New codon encodes a different amino acid & there is a change in amino acid sequence.
Nonsense mutation: New codon encodes a stop codon & thus premature termination of translation.
Silent mutation: New codon encodes same amino acid & there is no change in amino acid sequence.
In case of mutant 1 there is premature termination of translation. So, here nonsense mutation occurs. In mutant 2 after amino acid arginine (arg), different amino acid encoded. So, here missense mutation occurs. In case of mutant 3 also single amino acid change in nucleotide sequence happens. So, here also missense mutation occurs.
b) Base substitution, insertion or deletion can cause mutation. In base substitution alteration of single nucleotide occurs. In case of insertion & deletion change in the reading frame of DNA occurs (except insertion & deletion is any multiple of three nucleotides), i.e., frame shift mutation. It is highly likely that base substitution occurs in case of mutant 1 & mutant 3 & encodes a premature stop codon & changes the amino acid tyrosine (tyr) to histidine (his) respectively. But in case of mutant 2 it is highly likely that an insertion or deletion occur after arginine amino acid.
c) As the fourth mutation produce 50% more protein & leads to gain-of-function. In order to produce more protein stop codon require encoding at a later stage than in the wild type. So, mutation occurs at the stop codon of wild type (after thr).
Second Part:
a) In case of mutant 3 there is premature termination of translation. So, here nonsense mutation occurs. In mutant 2 after amino acid arginine (arg), different amino acid encoded. So, here missense mutation occurs. In case of mutant 1 also single amino acid change in nucleotide sequence happens. So, here also missense mutation occurs.
b) Base substitution, insertion or deletion can cause mutation. In base substitution alteration of single nucleotide occurs. In case of insertion & deletion change in the reading frame of DNA occurs (except insertion & deletion is any multiple of three nucleotides), i.e., frame shift mutation. It is highly likely that base substitution occurs in case of mutant 3 & mutant 1 & encodes a premature stop codon & changes the amino acid tyrosine (tyr) to cysteine (cys) respectively. But in case of mutant 2 it is highly likely that an insertion or deletion occur after arginine amino acid.
c) As the fourth mutation produce 50% more protein & leads to gain-of-function. In order to produce more protein stop codon require encoding at a later stage than in the wild type. So, mutation occurs at the stop codon of wild type (after thr).
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