7.012 Lecture Notes - Lecture 6: Arginine, Purine, Differential Centrifugation
Document Summary
Look at the arginine biosynthetic pathway: (cid:198) (cid:198) (cid:198) arginine. Biochemistry studying a single component in an organism. Genetics studying an organism without that component. The pathway involves the conversion of via two intermediates, and to arginine. The three steps in the conversion of to arginine are catalyzed by the three enzymes, a, B and c (genes a, b and c) Can have defects in any of the steps in the synthesis of arginine. With arginine in the medium, all arg mutants can grow on minimal medium. Given a set of arg mutants, you can determine which mutants have mutations in which genes (steps) in the pathway by testing the growth of mutants and looking at accumulations of intermediates in the pathway. Pathway and steps that are defective in each mutant: Arg1/arg3 x (double mutant: blocked in two steps) Epistasis is when the phenotype associated with an allele masks the expression of the phenotype associated with another allele.
