discover a mutant yeast strain that cannot grow when provided with pyruvate as its sole carbohydrate, although it grows normally when given glucose as a carbon energy source; you call this the Pyr- trait. Wild-type yeast can grow well using either carbon source; you designate this the Pyr trait. You suspect that the mutant yeast have defective mitochondria.
You want to determine whether the mutation responsible for the Pyr- trait is carried in the nuclear or mitochondrial genome. Your experiment is to mate Pyr- haploid cells to Per haploid cells and examine segregation of the trait in the progeny. After mating, the hybrid diploid cells can grow on pyruvate (Pyr+). You send these diploid cells through meiosis and examine the four haploid cells generated from a single diploid cell. If the mutation is in mitochondrial DNA, will the four haploid cells probably be all Pyr-, all Pyr, or a combination? What if the mutation is in nuclear DNA?