Can someone explain this whole thing to me as in why i dont understand it . For
ID: 205612 • Letter: C
Question
Can someone explain this whole thing to me as in why i dont understand it
. For qus 21 and 22, consider the pathway for the synthesis of the amino acid arginine (below) ARG-E ARG-F ARG-H ornithine citrulline -5) argininosuccinate arginine Mutant stra listed below. Strains may carr growth is shown by (o). ins of Neurospora are grown in minimal media containing one of the supplements s y more than one mutation. Growth is shown by +) and no Suppl ements mutant nothing onithine catrulline arginino arginine strain succinate 0 0 0 Both strains also accumulate ornithine. 21) Indicate the statement that is most correct regarding strain A. It has a mutation in ARG-E It has a mutation in ARG-F It has a mutation in ARG H It has a mutation in ARG-E&F-; B) C) E) It has a mutation in ARG-F &H; 22) Indicate the satement that is most corret regdi stB It has a mutation in ARG-E ) It has a mutation in ARG-F C) It has a mutation in ARG-H It has a mutation in ARG-E &F; E) It has a mutation in ARG-F & HyExplanation / Answer
If a mutant can grow in the presence of a supplement means that the mutation is located in a gene that acts on a step which is downstream to the synthesis of the supplement.
For example, mutant X can grow in the presence of nutrient N. It means that the reaction catalyzed by protein X is an earlier step to the biosynthesis of N.
In the given case, strain A can grow only in the presence of argininosuccinate and arginine. So, it must contain a mutation in upstream steps that produce argininosuccinate. These upstream steps are catalyzed by ARG-E and F. So, the mutation could be located in either of these genes.
Strain B can grow only in the presence of citrulline, argininosuccinate, and arginine. So, it must contain a mutation in upstream steps that produce citrulline. This upstream step is catalyzed by ARG-E. So, the mutation must be located in ARG-E gene.