Question

Strain Phenotype on YPD Phenotype on Minimal Wild type Aade2 Made4 Aade2 Aade4 2. (2 pts) The YPD plates contain a limited amount of adenine, which causes induction of the pathway to synthesize more. Mutation of the genes required for the pathway can lead to blockage at an intermediate stage of the reaction. Accumulation of a certain intermediate leads to a red coloration of the yeast in your Aade2 mutant. The order of the genes involved in the pathway can be inferred from the data in the table above. Which of the figures below is a possible representation of the correct gene order based on your observed data? ade2 ade4 A. Red Adenine ade4 ade2 Red Adenine B. ade4 ade2 Adenine C. Red ade2 ade4 Adenine D. Red

Answer 1

Mutation in ade 1 or ade 2 result in the formation of the red pigment by the oxidation of P-ribosylaminoimidazole or AIR. Any mutation that blocks the oxidation of AIR will result in white colonies. So mutstion upstream of ade 1 and 2 will result in white colonies as this will further inhibit the pathway. Option B is correct. ADE4 works upstream of the red pigment and ADE2 works downstream of the red pigment. Mutation in ade2 will lead to the accumulation of AIR which upon oxidation will lead to red colonies.