MICB 325 Study Guide - Quiz Guide: Tryptophan Synthase, Epistasis, Mhc Class I Polypeptide-Related Sequence B
Document Summary
1: as mentioned in topic 1 (section iii. c), some mutations in mutants partially or fully restore a wild type phenotype, but do not restore the wild type genotype. A pictorial example of one type is given below: We consider the details of only two of several possible intragenic suppression scenarios. Compensating mutation allows substrate to enter active site. Mutant enzyme with substrate unable to enter active site. Wild type enzyme with substrate in active site: point mutations: Tgg --> tga --> cga trp stop arg. In this hypothetical case a tryptophan codon was changed to a stop codon, but subsequent change of the stop codon to an arginine codon resulted in a functional protein. 5" atg tgg gga ccc aag ggt agc ccc 3" (wild type) met trp gly pro lys gly ser pro 5" atg tgg ggg acc caa ggg tag ccc c 3" (1 mutant) met trp gly thr gln gly stop: frameshift mutations:
