Arginine is synthesized in a pathway involving several enzymes and biosynthetic intermediates. Five Neurospora crassa strains were cultured on minimal media containing various additives, and the results are shown. Match each N. crassa strain with its description.

$$\begin{array} { | c | c | c | c | c | }
\hline & \text { glutamate } & \text { ornithine } & \text { citrulline } & \text { arginine } \
\hline \text { Strain A } & \text { growth } & \text { growth } & \text { growth } & \text { growth } \
\hline \text { Strain B } & \text { no growth } & \text { no growth } & \text { growth } & \text { growth } \
\hline \text { Strain C } & \text { no growth } & \text { no growth } & \text { no growth } & \text { no growth } \
\hline \text { Strain D } & \text { no growth } & \text { no growth } & \text { no growth } & \text { growth } \
\hline \text { Strain E } & \text { no growth } & \text { growth } & \text { growth } & \text { growth } \
\hline
\end{array}$$

Question

Arginine is synthesized in a pathway involving several enzymes and biosynthetic intermediates. Five Neurospora crassa strains were cultured on minimal media containing various additives, and the results are shown. Match each N. crassa strain with its description.

$$\begin{array} { | c | c | c | c | c | } 
\hline & \text { glutamate } & \text { ornithine } & \text { citrulline } & \text { arginine } \
\hline \text { Strain A } & \text { growth } & \text { growth } & \text { growth } & \text { growth } \
\hline \text { Strain B } & \text { no growth } & \text { no growth } & \text { growth } & \text { growth } \
\hline \text { Strain C } & \text { no growth } & \text { no growth } & \text { no growth } & \text { no growth } \
\hline \text { Strain D } & \text { no growth } & \text { no growth } & \text { no growth } & \text { growth } \
\hline \text { Strain E } & \text { no growth } & \text { growth } & \text { growth } & \text { growth } \
\hline
\end{array}$$

Quizplus · Accepted Answer

The Answer is Answer: Answers are shown in the following table. Strain C is defective in a different biosynthetic pathway, because supplementation with arginine does not rescue the growth phenotype. Note that strain A is also technically not defective in the arginine pathway, but shows normal growth so this is wild-type with respect to the conditions under consideration here. The remaining strains can grow if they are provided with a supplement that occurs after the enzyme defect in the pathway. Thus, growth in strain E with ornithine, citrulline, and arginine but not with glutamate indicates that the defect is in enzyme 1.

\begin{array} { | c | c | c | c | c | c | } \hline & ext { glutamate } & ext { ornithine } & ext { citrulline } & ext { arginine } & \\hline ext { Strain A } & ext { growth } & ext { growth } & ext { growth } & ext { growth } & ext { Wild-type } \\hline ext { Strain B } & ext { no growth } & ext { no growth } & ext { growth } & ext { growth } & ext { defective in enzyme 2 } \\hline ext { Strain C } & ext { no growth } & ext { no growth } & ext { no growth } & ext { no growth } & \begin{array} { c } ext { not defective in the } \ ext { arginine biosynthesis } \ ext { pathway }\end{array} \\hline ext { Strain D } & ext { no growth } & ext { no growth } & ext { no growth } & ext { growth } & ext { delective in enzyme 3 } \\hline ext { Strain E } & ext { no growth } & ext { growth } & ext { growth } & ext { growth } & ext { defective in enzyme 1 } \\hline\end{array}

Arginine Is Synthesized in a Pathway Involving Several Enzymes and Biosynthetic