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: $\begin{array}{c}\text { ornithine } \stackrel{\text { ARG-E }}{\rightarrow} \text { citrulline } \stackrel{\text { ARG-F }}{\rightarrow} \text { argininosuccinate } \stackrel{\text { ARG-H }}{\rightarrow} \text { arginine }\end{array}$
Mutant strains of Neurospora are grown in minimal media supplements as follows.The strains may carry more than one mutation.Growth is shown by (+) and no growth is shown by (o) . $\begin{array}{cccccc}&&&\text { Supplements }\\\text { mutant } & \text { nothing } & \text { ornithine } & \text { citrulline }&\text { arginino- } & \text { arginine } \\\text { strain } & &&&{\text { succinate }} \\\mathrm{a} & 0 & 0 & 0 & + & + \\\mathrm{b} & 0 & 0 & + & + & +\end{array}$
Strain a accumulates citrulline,strain b does not.Indicate the statement that is most correct regarding these two strains.

A) Strain a has a mutation in ARG-E only.
B) Strain b has only one mutation.
C) Strain a has mutations in ARG-F and ARG-H.
D) Strain a has mutations in ARG-E,ARG-F and ARG-H.
E) Strain a has a mutation in ARG-H only.