The genetic components of biochemical pathways have often been identified using
ID: 64383 • Letter: T
Question
The genetic components of biochemical pathways have often been identified using mutant analysis. Several different mutants of Neurospora unable to completely breakdown the amino acid Phenylalanine have been isolated. Five such mutants, each from a different complementation group, were investigated to determine what role each gene plays in the pathway. The biochemical pathway of phenylalanine breakdown is attached. Each mutant was supplied different intermediates of the pathway, and then observed for the production of carbon dioxide. Answer the following questions.
a. This work is similar to the work of Beadle and Tatum. What theory did their experiments lead to?
b. Beadle and Tatum worked with mutants that could not grow in the absence of arginine. What term describes mutants that are unable to grow in the absence of a particular substance?
c. If all these mutants did belong to the same complementation group, what would that mean?
d. Indicate which mutant corresponds to which enzyme from the biochemical pathway chart
e. In humans, the disease alcaptonuria is also known as “Black Urine” disease, and is due to a build-up of homogentisic acid in the urine. Which mutant gene in Neurospora corresponds to the same dysfunctional gene in human sufferers of alcaptonuria
Phenylalanine
enzymeA
Tyrosine
enzymeB
p-Hydroxyphenylpyruvate (PHPP)
enzymeC
Homogentisic acid (HA)
enzymeD
Maleylacetoacetic acid (MAA)
enzymeE
CO2 and H2O
HA maa phenylalanine phpp tyrosine mutant 1 + + - - - mutant 2 - - - - - mutant 3 - + - - - mutant 4 + + - + + mutant 5 + + - + -
Explanation / Answer
The arg1 genes encode a compound, ARG1, important to change over N-acetylornithine into one of alternate intermediates and these chemical capacities ahead of schedule in the pathway. The arg2 genes encodes a catalyst important to change over ornithine into one of alternate intermediates and this chemical capacities next in the pathway.
N-acetylornithine -- ARG1-------> ornithine -- ARG2-------> citrulline -- ARG3-------> arginosuccinate --- ARG4------> arginine
The double mutant ought to just develop on insignificant media supplemented with citrulline, arginosuccinate, or arginine.
e. answer : Phenylalanine
enzymeA
Tyrosine
enzymeB
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