Several mutants are isolated, all of which require compound G for growth. The compounds (A to E) in the biosynthetic pathway to G are known, but their order in the pathway is not known. Each compound is tested for its ability to support the growth of each mutant (1 to 5). In the following table, a plus sign indicates growth and a minus sign indicates no growth. Compound tested A B C D E G Mutant 1 - - - + - + 2 - + - + - + 3 - - - - - + 4 - + + + - + 5 + + + + - + a. What is the order of compounds A to E in the pathway? b. At which point in the pathway is each mutant blocked? c. Would a heterokaryon composed of double mutants 1,3 and 2,4 grow on a minimal medium? Would 1,3 and 3,4? Would 1,2 and 2,4 and 1,4?
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Several mutants are isolated, all of which require compound G for growth. The compounds (A to E) in the biosynthetic pathway to G are known, but their order in the pathway is not known. Each compound is tested for its ability to support the growth of each mutant $(1 mathrm{to}$ 5). In the following table, a plus sign indicates growth and a minus sign indicates no growth. a. What is the order of compounds A to E in the pathway? b. At which point in the pathway is each mutant blocked? c. Would a heterokaryon composed of double mutants 1,3 and 2,4 grow on a minimal medium? Would 1,3 and $3,4 ?$ Would 1,2 and 2,4 and $1,4 ?$
Dominador T.
Let's assume that you have isolated five mutants in Neurospora crassa (#1 to #5) that cannot synthesize a compound essential for growth. You, being such a bright individual, also know the compounds (A through F) that are required in the biosynthetic pathway of compound F. However, you do not know the order in which these intermediates are synthesized by the wild-type cells that grow on minimal medium. To figure this out, you decide to test each mutant for its ability to grow when supplemented with each intermediate compound. Your results are as follows: a plus sign means growth, and a minus sign means no growth. Compound Tested Mutant Determine the order of compounds in the biochemical pathway and indicate which step in the pathway is affected by each mutation. Your answer should follow the format given below: ~F BUT this is NOT the right answer.
Madhur L.
After treating cells with a chemical mutagen, you isolate two mutants. One carries alanine and the other carries methionine at a site in the protein that normally contains valine (Figure $\mathbf{Q} 6-3$ ). After treating these two mutants again with the mutagen, you isolate mutants from each that now carry threonine at the site of the original valine (Figure Q6-3). Assuming that all mutations involve single nucleotide changes, deduce the codons that are used for valine, methionine, threonine, and alanine at the affected site. Would you expect to be able to isolate valine-to-threonine mutants in one step?
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