Final answer:
The 7 different arg- mutants were tested for growth in the presence of intermediates in the arginine biosynthesis pathway. Each mutant differed in their ability to grow depending on the specific intermediate added to the minimal medium.
Step-by-step explanation:
The 7 different arg- mutants were tested for growth in the presence of intermediates in the arginine biosynthesis pathway. Each mutant differed in their ability to grow depending on the specific intermediate added to the minimal medium. By observing the growth patterns, Beadle and Tatum were able to identify three classes of mutants that had defects in different genes within the arginine biosynthesis pathway.