In yeast, there are three gene products required to synthesize the amino acid lysine. You cross two haploid lysine auxotrophs to form a diploid. The diploid fails to grow on plates lacking lysine. Which of the following can you definitively conclude?
A) The haploid strains have identical mutations in the same genes.
B) The haploid strains must belong to the complementation group encoding the first enzyme in the biosynthetic pathway.
C) The haploid strains have identical mutations in different genes.
D) The haploid strains have mutations in the same gene.
E) The haploid strains have mutations in different genes.

Question

Quizplus · Accepted Answer

The diploid's inability to grow on lysine-free media indicates that both haploid strains have mutations in the same gene, preventing complementation and thus lysine synthesis.

In Yeast, There Are Three Gene Products Required to Synthesize