Answer:
As we all know that yeast is a unicellular organism (a fungus) which has a asexual mode of reproduction and that through mitosis hence resulting in the production of two identical daughter cells.
Now, it can enter a meiotic pathway and thus form either spores or haploid cells providing the mother cell is diploid. The two haploid cells can mate and become diploid.
Now according to the question, if there is a mutation in yeast cell it will result in the exclusion of protein needed for biosynthesis which can no longer survive in growth medium.
1 gene co-relates to 1 protien and the genotype is often shown in its phenotype, find mutants which do not detect odour/ smell.
Lets provide a simple example here.
As we look at arginine biosynthesis yeast model: