Twelve recessive proline auxotrophs in Neurospora were isolated in a mutant screen. These mutants do not grow on minimal medium. Pairwise crosses were performed and the diploid F1 were tested for growth on minimal medium. The table below shows the result of these crosses, where (+) indicates growth and (-) indicates no growth on minimal medium.

A. (4 pts) How many different genes were identified in this mutant screen?
gene(s)

B. (12 pts) List the mutants defective in each gene. (Use “-” to link mutants in the same gene, use “,” to separate each gene. For example: 1-2, 3-4, 5-6-7)

C. (4 pts) Fill in the gray squares of the table with the expected result. Indicating a (+) for growth and a (-) if no growth.