You discover a mutant yeast strain that cannot grow whenprovided with pyruvate as its sole carbohydrate, although it growsnormally when given glucose as a carbon energy source; you callthis the Pyr– trait. Wild-type yeast can grow well using eithercarbon source; you designate this the Pyr+ trait. You suspect thatthe mutant yeast have defective mitochondria.
A. Why is mitochondrial function critical forgrowing on pyruvate?
B. You want to determine whether the mutationresponsible for the Pyr– trait is carried in the nuclear ormitochondrial genome. Your experiment is to mate Pyr– haploid cellsto Pyr+ haploid cells and examine segregation of the trait in theprogeny. After mating, the Pyr-/Pyr+ diploid cells can grow onpyruvate (Pyr+). You send these diploid cells through meiosis andexamine the four haploid cells generated from a single diploidcell. If the mutation is in mitochrondrial DNA, will the fourhaploid cells probably be all Pyr–, all Pyr+, or a combination?What if the mutation is in nuclear DNA?
