Consider the Pathway for the Synthesis of the Amino Acid

Multiple Choice

Consider the pathway for the synthesis of the amino acid arginine in Neurospora: $\begin{array}{ll}&A R G-E&&A R G-F&&A R G-H\\\text { ornithine }& \rightarrow &\text { citrulline } &\rightarrow& \text { argininosuccinate } &\rightarrow&\text { arginine }\end{array}$
Mutant strains of Neurospora may carry one or more mutations.Neurospora mutant strain a is grown on minimal media plus supplements as shown.Growth is shown by (+) and no growth is shown by (o) .Growing strain a cells accumulate citrulline. $~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~\text { Supplements }$
$\begin{array}{ccccc}\begin{array}{c}\text { mutant } \\\text { strain }\end{array} & \text { nothing } & \text { ornithine } & \text { citrulline } &\begin{array}{c}\text { arginino-}\\\text { succinate }\end{array}&{ arginine }\\a&0&0&0&0&+\end{array}$ Which statement is true about strain a?

A) It has one mutation in ARG-H.
B) It has two mutations, one in ARG-F and one in ARG-H.
C) It has two mutations, one in ARG-E and one in ARG-H.
D) It has two mutations, one in ARG-E and one in ARG-F.
E) It has mutations in ARG-E, ARG-F, and ARG-H.