Lecture.15.Fall.2013(1)

Genetic analysis of biochemical pathways hypothesis

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Unformatted text preview: grew only on arg - neither cit nor orn could substitute • What can we deduce about the biochemical pathway these mutants affect? Genetic Analysis of Biochemical Pathways • Hypothesis: Each mutation creates a “block” in a biosynthetic pathway by inactivating an enzyme in that pathway • If we supplement with a substance that is after the block, the other (wildtype) enzymes can complete the pathway • What is the final product of the pathway? Genetic Analysis of Biochemical Pathways • Since all mutant strains can grow w/arg supplementation, arg is AFTER all of the blocks in the pathway. • Some mutants will grow with cit, but not orn • In these mutants, the block is after orn, but before cit • Some mutants will grow with any of the three supplements • In these strains, the block is before any of the three compounds Genetic Analysis of Biochemical Pathways • Next: where in the pathway do the genes function? • arg1 is required to convert cit to arg • arg2 and 3 are required to convert orn to cit • arg4-7 are are required before orn So: Precursor(s) arg4-7 ornithine arg...
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