Question

You are studying an interesting protein in nematode worms that is 100 amino acids in length. Of particular interest is the fact that the last seven amino acids are all tryptophan (codons 94 through 100). Draw here the mRNA sequence for codons 94-100: Draw here the sequence of the DNA strand RNA polymerase used as its template (show 5' 3' polarity): You mutagenize the wild type worm. Assume for the next questions you are able to isolate both normal and mutant types of the protein and generate amino acid sequence. A fir mutant protein is 100 amino acids in length. The only change in sequence from wild type is that amino acid #100 is now arginine. Name the mutation type and explain the mutation as the codon change in the mRNA: You mutagenize the wild type again, and now recover a new mutant protein. It's 93 amino acids in length, and those 93 amino acids arc wild type in sequence. Name the mutation type and explain the mutation as the codon change in the mRNA: You mutagenize the wild type again and recover this time another new mutant protein. It's 103 amino acids in length. The first 97 amino acids are wild type in sequence, but here's the amino acid sequence from amino acids 98-103: -M-V-V-V-M-M-COOH Name the mutation type and explain the mutation at the level of mRNA change:

Answer 1

4)

a)

The amino acid tryptophan is encoded by the codons, namely UGG only.

The mRNA sequence is as follows:

5’-UGGUGGUGGUGGUGGUGGUGG-3’

b)

The DNA strand that is used by the RNA polymerase is as follows:

5’- TGGTGGTGGTGGTGGTGGTGG -3’

c)

This type of mutation is a called missense mutation. In this condition, the TGG (code for tryptophan) is changed into AGG (code for arginine).

d)

This type mutation is called Non-sense mutation. In this condition, the 94^th codon TGG is mutated into TAG. It is a stop codon, so the protein is abruptly truncated.

e)

This type of mutation is called insertion. In this condition, insertion of a single nucleotide or more than one nucleotide will change the reading frame.