8-9 Which gene (C or D) is downstream in the pathway based on the epistatic class for feeding behavior? Gene C gene D Feeding Experiment: If methionine is added to the growth media of these mutant strains, all of them can grow. Some of them can intermediates in the synthesis of methionine are added. The intermediates include homocysteine, cysteine and cystathionine. In the table below the growth behavior (+ or -) of the methionine auxotrophs are shown when each strain is fed different compounds. Using this table, order the synthesis of intermediates from first to last in the synthesis of methionine Order of intermediates: ---- rightarrow _________ ---- rightarrow _________ ---- rightarrow _________ methionine Above each arrow indicate where each mutant (met A, B or Cor D) belongs. ---- rightarrow _________ ---- rightarrow _________ ---- rightarrow _________ methionine What intermediate builds up in the met A strain? _________ what intermediate builds up in the met C strain? __________ What intermediate builds up in the met D strain? Solution 1.The gene D is downstream in the process. 2.cysteine - cystathionine - homocysteine - methionine. 3.The first arrow represent strain B, the second arrow represent strain C, the third arrow represent strain D and fourth arrow represent strain A..