D. AUGGGCGGAGCCGCGAUAG Frameshift mutation 5. You are studying a mutation in mic

Question

D. AUGGGCGGAGCCGCGAUAG Frameshift mutation 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 gainof-function and what specific subtype (hvpermorphic, antimorphiç, 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.

Explanation / Answer

Ans 5. Kinky-tail in mice is a mutation that leads to the dysmorphology of the tail. Due to this mutation, vertebral fusions occur that disrupt the general morphology of the tail. This mutation is a loss-of function, because the general functions that are otherwise performed by a normal tail gets hindered due to this type of tail. Only heterozygous individuals survive with such mutations, the homozygous individuals die early in the embryonic stage.

The heterozygous individuals with the kinky tail show hypermorphic subtype beacuse there are varied type of morphology available with the mice showing such type of mutations.

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