Suppose That a Mutant Organism Is Unable to Make the Amino

Multiple Choice

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?

A) citrulline to arginosuccinate
B) arginosuccinate to arginine
C) ornithine to citrulline
D) ornithine to arginosuccinate