You are studying mutations in a bacterial gene that codes for an enzyme whose amino acid sequence is known. In the wild type protein, proline is the 5th amino acid from the amino terminal end. In one of your mutants with nonfunctional enzyme, you find a serine at position number 5. You subject this mutant to further mutagenesis and recover 3 different strains. Strain A has a proline at position 5 and acts just like the wild-type strain. Strain B has tryptophan at position number 5 and also acts like wild type. Strain C has no detectable enzyme function at any temperature, and you can't recover any protein that resembles the enzyme. You mutagenize strain C and recover a strain ( C-1) that has enzyme function. The second mutation in C-1 that is responsible for the recovery of enzyme function does not map at the enzyme locus. a) What is the nucleotide sequence in both strands of the wild-type gene at this location? b) Why does strain B have a wild-type phenotype? Why does the original mutant with serine at position 5 lack function? c) What is the nature of the mutation in strain C?
You are studying mutations in a bacterial gene that codes for an enzyme whose amino acid sequence is known. In the wild type protein, proline is the 5th amino acid from the amino terminal end. In one of your mutants with nonfunctional enzyme, you find a serine at position number 5. You subject this mutant to further mutagenesis and recover 3 different strains. Strain A has a proline at position 5 and acts just like the wild-type strain. Strain B has tryptophan at position number 5 and also acts like wild type. Strain C has no detectable enzyme function at any temperature, and you can't recover any protein that resembles the enzyme. You mutagenize strain C and recover a strain ( C-1) that has enzyme function. The second mutation in C-1 that is responsible for the recovery of enzyme function does not map at the enzyme locus. a) What is the nucleotide sequence in both strands of the wild-type gene at this location? b) Why does strain B have a wild-type phenotype? Why does the original mutant with serine at position 5 lack function? c) What is the nature of the mutation in strain C?
