Consider the Pathway for the Synthesis of the Amino Acid

question 44

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.Each mutant strain carries only a single mutation.Growth is shown by (+) ,no growth is shown by (o) . $\begin{array}{cccccc}&&&\text { Supplements }\\\text { mutant } & \text { nothing } & \text { ornithine } & \text { citrulline }&\text { arginino- } & \text { arginine } \\\text { strain } & &&&{\text { succinate }} \\\mathrm{a} & 0 & 0 & 0 & + & + \\\mathrm{b} & 0 & 0 & + & + & + \\\mathrm{c} & 0 & 0 & 0 & 0 & +\end{array}$
Indicate the correct pairing: mutant strain defective gene.

• A) strain a ARG-F
• B) strain a ARG-H
• C) strain b ARG-F
• D) strain c ARG-E
• E) strain c ARG-F

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Definitions:

Sensory Adaptation

The process by which sensory receptors become less sensitive to constant or unchanging stimuli over time, allowing individuals to focus on changes in their environment.

Absolute Threshold

The lowest level of stimulation that an organism can detect at least 50% of the time.

Attention

The process of sorting through sensations and selecting some of them for further processing.

Difference Threshold

The smallest difference in stimulus intensity required to detect a difference between two stimuli, also known as the just noticeable difference (JND).