Now, figure out the complementation groups. This shows how many genes are involved in this pathway. Some of the mutant classes in the previous problem must contain more than one complementation group (gene) For example class 2 is defined by mutants 1,3,4,6, and 7. These mutants may, or may not, all be in the same gene. Complementation testing will help you know if they are, or are not, in the same gene. So there are actually additional steps between some of the letters. For example, maybe instead of XàY, it is really XàFàGàY.
Extracted text: (c) The singi CHALLENGE PROBLEM 2 You are carrying out Beadle Tatum type experiments to analyze a metabolic pathway in Neurospora. You know that the precursor in the pathway is a molecule symbolized as P and that the product is a vitamin symbolized as Z. You are sure that the pathway from P to Zis linear and that the molecules W, X, and Y are intermediates. However, there may be other intermediates not yet identi- fied. You obtain 10 independent mutations that cannot grow on minimal medium supplemented with P, but can grow on minimal medium supplemented with Z. The 10 mutants fall into four classes that can grow (+) or cannot grow (-) on minimal medium supplemented with the nutrients W, X, or Y. The data are shown in the accompanying table. P W X Y Z Class I (mutant 5) Class II (mutants 1, 3. 4. 6, 7) Class III (mutant 2) Class IV (mutants 8, 9, 10) Draw a linear metabolic pathway with P on the left and Z on the right, in which each of the intermediates W, X, and Y is shown in the order in which it occurs in the metabolic pathway in the synthesis of Z from P.
Extracted text: CHALLENGE PROBLEM 3 The 10 mutants in Challenge Problem 2 were tested for complementation in all pairwise combinations using heterokaryons. The results are shown in the matrix, in which + indicates the ability of the hetero- karyon to grow in minimal medium and – indicates inabil- ity to grow in minimal medium. 2 3 4 5 6 7 8 9. 10 Mutant 1 + + + + + 3. + + + + + + + 6. + + 7 8. 6. Assume that each complementation group defines a different gene, and assume further that each gene encodes an enzyme that catalyzes a single step in the metabolic pathway, which converts one molecule of substrate into one molecule of product. (a) Redraw the metabolic pathway deduced from Chal- lenge Problem 2. Use a right arrow to indicate each enzymatic step in the pathway, and label each arrow with the mutant number 1-10 that blocks the enzy- matic step. In some cases, you will not be able to specify the order in which the enzymes occur in the pathway, so you may write them in any order you wish. (b) In the metabolic pathway that you have deduced from the data, how many unknown intermediates are there between the precursor P and the vitamin Z? + + + + + +十 + + + 2.