Question

34. (6 points) Currently you are studying threonine synthesis in yeast. To find genes whose protein products are important for threonine synthesis, you perform a mutagenesis to find mutants that require a source of threonine to grow. You find a total of nine mutants, all of which have recessive phenotypes. You perform complementation tests with all of your mutants. Below are the results for your complementation tests. A (+) means growth and a() means no growth: mtl mt2mt3m4 mt mt mt mt mt w mtl mt2 mt3 mt4 + - + - + + - mt mtb mt7 + + + + mt8 + mt9 Wt (a) How many complementation groups did you identify? (b) For each complementation group, indicate which mutants belong to that complementation group. You have identified some intermediates in threonine synthesis: A, B, C, D and E. You grow a few of your mutants in the presence of these different intermediates to determine the order in which the gene products act. Below are your results. A (+) means growth and a (-) means no growth C D E Threonine Mti Mt2 M14 M7 (c) Given these data, draw the best possible pathway for the synthesis of threonine. The diagram should use arrows to indicate one intermediate being changed to another intermediate. Indicate which gene produces the product responsible for the conversion by listing the mutant in that gene above the arrow. For example, if the gene product that is mutant in mt8 is responsible for converting A to B, that would be drawn as: mt8

Answer 1

All the parts are explained in Handwritten solution. Please find the attached solution:

Solh :-34. (a) Total a complementation groups are present. (b). Complementation group 1 - 1,3,5,6,9 Complementation group 2 = 9,8 & ie. In each of these two compartment group , mutants will never complement each other or o 1,3,5,6,9 - will never complement for each other & thus mutant will form. © 2,8 → no complementation > Mutent will remain (@) A mtl D Mt 7 c Mitle Ble Mtz, Threonine. e In the pathway of synthesis of threonine, A, D, C,Ble are intermediates. If we provide mt1, D will from from A. then with the help of Mit 7 , I will form. Finally, by providing mt 4 & m+ 2 , threonine will foom.