Suppose that a mutant organism is unable to make the amino acid arginine. Knowing that the metabolic pathway to production of arginine is ornithine - citrulline - arginosuccinate -arginine, you test the ability of the mutant to grow in the presence of each one of these compounds, providing just one of the compounds in each of your tests. Also suppose that you find that the mutant can grow in the presence of arginosuccinate or arginine, but NOT in the presence of citrulline or ornithine. From this information, which step in the metabolic pathway do you think is blocked?

Question

Quizplus · Accepted Answer

The mutant can grow when arginosuccinate or arginine is provided, indicating that the block is before arginosuccinate. Since it cannot grow with citrulline, the block is at the step converting citrulline to arginosuccinate.

Suppose That a Mutant Organism Is Unable to Make the Amino