[Campbell Biology P.385] A Neurospora mutant is obtained following Beadle and Tatum's experi... | Practice Question

A Neurospora mutant is obtained following Beadle and Tatum's experimental approach. When this mutant is grown on minimal medium supplemented with valine, lysine, or arginine, it only shows growth on the minimal medium supplemented with arginine. Based on Figure 17.2 and the accompanying text, what can be concluded about this specific mutant?

  • A: This mutant has a defective gene for synthesizing arginine.
  • B: This mutant is wild-type and can synthesize all necessary nutrients.
  • C: This mutant requires all three amino acids (valine, lysine, and arginine) for growth.
  • D: This mutant is missing the enzyme for synthesizing valine.

Explanation

According to step 6 of Figure 17.2, if a mutant grows only on minimal medium supplemented with a specific nutrient e.g., arginine , it indicates that the mutant is missing the enzyme for the synthesis of that particular nutrient. Thus, the mutant has a defective gene for synthesizing arginine.