Suppose that you performed a cross of a wild type strain of Neurospora to a strain with a defective synthesis of the amino acid tryptophane. You dissect asci and test each spore individually for the ability to develop into a colony on the minimal medium without tryptophane. What proportion of these spores do you expect to grow on the minimal medium

Explanation:

Given;

Cross between a wild type stain of Neurospora  and mutant stain.

Wild type can grow on minimal medium too.

Mutant strain is defective in synthesis of tryptophane amino acid. So, mutant strain can grow only in complete medium, and it can not grow on minimal medium, while wild type can grow in both mediums.

So after crossing both stains, half spores get defective gene while half get normal gene, so 1/2 or 50% proportion can  grow on minimal medium.