Practice question

Linear pathway A to E ordered by observing which supplements rescue growth of mutant blocked between C and D, applying bypass logic. Upstream intermediates A and B require functional conversion through blocked enzyme so they fail to restore growth because defect remains. Downstream products D and E bypass defect directly supplying end product for protein synthesis. Some textbooks include immediate precursor C as rescuing if accumulation drives leaky activity but principle remains downstream rescue indicates block position. Counting rescued mutants per supplement allows sequential arrangement of metabolites reflecting enzyme order along chromosome.