The table shows the biochemical pathway of arginine production and growth of Neurospora under various conditions. Wild-type Neurospora was treated with X-rays to induce heritable mutations.Treated Neurospora was grown on minimal medium ("no addition" in the table) and minimal medium supplemented with the compounds indicated in the table.Growth is indicated as dry weight of fungal material after 5 days.Here we see the results of three mutated strains that were linked to the metabolic pathway that generates arginine.Without arginine production, Neurospora cannot grow.

Considering the biochemical pathway of arginine production, what explanation could account for the ability of strains 34105 and 33442 but the inability of strain 36703 to show some growth on minimal medium?
A) The minimal medium was contaminated with arginine.
B) The minimal medium was contaminated with low levels of citrulline.
C) The minimal medium was contaminated with low levels of ornithine.
D) The minimal medium was contaminated with low levels of the precursor.
E) Another metabolic pathway provided low levels of arginine.

Question

The table shows the biochemical pathway of arginine production and growth of Neurospora under various conditions.

Wild-type Neurospora was treated with X-rays to induce heritable mutations.Treated Neurospora was grown on minimal medium ("no addition" in the table) and minimal medium supplemented with the compounds indicated in the table.Growth is indicated as dry weight of fungal material after 5 days.Here we see the results of three mutated strains that were linked to the metabolic pathway that generates arginine.Without arginine production, Neurospora cannot grow.

Considering the biochemical pathway of arginine production, what explanation could account for the ability of strains 34105 and 33442 but the inability of strain 36703 to show some growth on minimal medium?

Considering the biochemical pathway of arginine production, what explanation could account for the ability of strains 34105 and 33442 but the inability of strain 36703 to show some growth on minimal medium?
A) The minimal medium was contaminated with arginine. 
B) The minimal medium was contaminated with low levels of citrulline. 
C) The minimal medium was contaminated with low levels of ornithine. 
D) The minimal medium was contaminated with low levels of the precursor. 
E) Another metabolic pathway provided low levels of arginine.

Quizplus · Accepted Answer

Strains 34105 and 33442 were able to produce some growth on minimal medium because they are still able to produce some citrulline through the mutated pathway, which can then be converted to arginine downstream. This suggests that the minimal medium may have been contaminated with low levels of citrulline, allowing for some growth. However, strain 36703 was unable to produce any growth, suggesting that the mutation in this strain completely blocked the pathway and no precursor or alternative pathway provided enough arginine for growth.

The Table Shows the Biochemical Pathway of Arginine Production and Growth