Consider the pathway for the synthesis of the amino acid arginine in Neurospora:
ID: 254539 • Letter: C
Question
Consider the pathway for the synthesis of the amino acid arginine in Neurospora: ARG-E ARG-F ARG-H ornithine citrulline -> argininosuccinate-arginine 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) Supplements mutant nothing ornithine citrulline arginino arginine strain succinate 0 0 0 0 0 0 Indicate the correct pairing: mutant strain defective gene. strain a ARGFExplanation / Answer
Answer:
Based on the given data:
Mutant strain "a" is unable to grow in the absence of ornithine and citrulline and only grows in presence of argino-succinate or arginine. Since each strain contains only single mutation, therefore, this indicates that the defective gene in mutant strain "a" is Arg-F. So correct pair for mutant "a" strain a / ARG-F. In the presence of Ornthine strain "a" is able to convert ornithine to citrulline because Arg-E gene product enzyme is functional but it is not able to transform citrulline to argininosuccinate due to defective Arg-F enzyme product. Due to this, the mutant strain "a" is not able to synthesize argininosuccinate and Arginine and doesnt grow when only ornthine and citrulline are added.
Mutant strain "b" is unable to grow when supplemeneted with Ornithine but is able to grow when Citrulline, argino-succinate or arginine is added. This indicates that the defective gene in mutant strain "b" is Arg-E. So correct pair for mutant "b" strain is strain b / ARG-E
Mutant strain "c" is unable to grow when all supplments are added except Arginine. It is able to grow in presence of arginine. This indicates that the defective genes in mutant strain "c" is Arg-F. So correct pair for mutant "c" strain is strain c / ARG-F
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