5. You are studying a mutation in mice, which acts dominantly. Mice that have only one copy of
the allele carrying this mutation have a kinky tail phenotype You identify the gene that the
mutation affects and find that the codon that encodes the second amino acid in the predicted
protein has been mutated to a stop codon. Would you characterize this mutation as a loss-of-
function or a gain- of-function and what specific subtype (hypermorphic, antimorphic, etc. )
within these categories? Explain your reasoning 6. You are following up on some of Yanofsky\'s
tryptophan synthetase mutants Since the time of his studies, we now know that the only function
of tryptophan synthetase is to synthesize tryptophan. It does not have another function in the cell.
You are studying two dominant mutations in tryptophan synthetase that Yanofsky discovered
(note that since these are bacteria, they only have a single copy of the gene normally, but if you
introduce a wild-type copy it does not rescue the phenotype). One of these, the \"A\" mutation
causes a huge amount of tryptophan to be formed within cells, resulting in decreased survival of
bacteria with this mutation. The other mutation, the \"B\" mutation causes the mutant tryptophan
synthetase to specifically degrade tRNAs within the cell, leading also to decreased survival of
bacteria. Please provide a categorization of what type of loss-of-function or gain-of-function
mutation the A and B mutations are and justify your answer
Solution
5. Mutation cause loss of function and the protein of lesser polypeptide length is formed. The
function is partially lost and protein is lesser functional called hypomorphic mutation.
6. Mutant A will having hypermorphic mutation giving gain of function and more protein will
formed. But mutant B will be having neomorphic mutation which will produce a newer type of
protein with altered function and new protein will cause decrease the survival rate by loss of
funtion.
the allele carrying this mutation have a kinky tail phenotype You identify the gene that the
mutation affects and find that the codon that encodes the second amino acid in the predicted
protein has been mutated to a stop codon. Would you characterize this mutation as a loss-of-
function or a gain- of-function and what specific subtype (hypermorphic, antimorphic, etc. )
within these categories? Explain your reasoning 6. You are following up on some of Yanofsky\'s
tryptophan synthetase mutants Since the time of his studies, we now know that the only function
of tryptophan synthetase is to synthesize tryptophan. It does not have another function in the cell.
You are studying two dominant mutations in tryptophan synthetase that Yanofsky discovered
(note that since these are bacteria, they only have a single copy of the gene normally, but if you
introduce a wild-type copy it does not rescue the phenotype). One of these, the \"A\" mutation
causes a huge amount of tryptophan to be formed within cells, resulting in decreased survival of
bacteria with this mutation. The other mutation, the \"B\" mutation causes the mutant tryptophan
synthetase to specifically degrade tRNAs within the cell, leading also to decreased survival of
bacteria. Please provide a categorization of what type of loss-of-function or gain-of-function
mutation the A and B mutations are and justify your answer
Solution
5. Mutation cause loss of function and the protein of lesser polypeptide length is formed. The
function is partially lost and protein is lesser functional called hypomorphic mutation.
6. Mutant A will having hypermorphic mutation giving gain of function and more protein will
formed. But mutant B will be having neomorphic mutation which will produce a newer type of
protein with altered function and new protein will cause decrease the survival rate by loss of
funtion.
