Five different uracil auxotrophs of Neurospora, a eukaryotic mold, are tested fo
ID: 208787 • Letter: F
Question
Five different uracil auxotrophs of Neurospora, a eukaryotic mold, are tested for growth on uracil and uracil precursors. The data are shown in the following table. A plus sign (+)means growth (assume each mutant has a single recessive mutation). Supplemented Compound A B C D Uracil Mutant 1 Mutant 2 Mutant 3 Mutant 4 Mutant 5 What is the order of compounds in the uracil biosynthetic pathway? C-> D-> A-> B-> Uracil A-> B-> C-> D:) Uracil B-> C>D-> A> Uracil B-> C-> D-> A-> UracilExplanation / Answer
Option B is correct. A> B> C> D
D compound is the final compound in the pathway which is required for uracil synthesis.
As you could see in mutants 2 that it couldn't convert the compound A, B, C due to a mutation in those enzyme which is required for conversion. But whereas when they gave D compound it survived. It means the enzyme responsible for the conversion of D to uracil is not mutated and it's the final step in the process. And all mutant 1,2,3,5 must contain an active enzyme (without mutation) to convert the D to uracil and hence you could see + sign in all the D compound for these mutant.
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