Fill in the blank. Another name for a genetic screen is a ______ screen.

Tryptophan is an essential amino acid that Neurospora crassa needs in order to be able to grow. The tryptophan biosynthetic pathway has three main steps by which the amino acid tryptophan is produced from chorismate. In an experiment, three N. crassa strains that were suspected of having defects in tryptophan synthesis were cultured on minimal medium (without tryptophan) and on minimum medium (plus tryptophan), with the following results. Which strain is defective in the tryptophan biosynthetic pathway?
$$\begin{array} { | l | c | c | } \hline & \text { Minimal medium } & \begin{array} { c } \text { Minimal medium } \\+ \text { tryptophan }\end{array} \\\hline \text { Strain 1 } & \text { no growth } & \text { growth } \\\hline \text { Strain 2 } & \text { no growth } & \text { no growth } \\\hline \text { Strain 3 } & \text { growth } & \text { growth } \\\hline\end{array}$$

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.
$$\begin{array} { | c | c | c | c | c | } \hline & \text { glutamate } & \text { ornithine } & \text { citrulline } & \text { arginine } \\ \hline \text { Strain A } & \text { growth } & \text { growth } & \text { growth } & \text { growth } \\ \hline \text { Strain B } & \text { no growth } & \text { no growth } & \text { growth } & \text { growth } \\ \hline \text { Strain C } & \text { no growth } & \text { no growth } & \text { no growth } & \text { no growth } \\ \hline \text { Strain D } & \text { no growth } & \text { no growth } & \text { no growth } & \text { growth } \\ \hline \text { Strain E } & \text { no growth } & \text { growth } & \text { growth } & \text { growth } \\ \hline \end{array}$$ " class="answers-bank-image d-block" loading="lazy" >

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