Question

Yeast mitochondria have a tubular morphology. In a mutagenic screen, two mutants are isolated that have fragmented mitochondria instead of tubular mitochondria. To determine if these two mutations are at the same or different loci, the two mutants are crossed. The progeny all have tubular mitochondria. What do you conclude?

Answer 1

The observation that all progeny have tubular mitochondria after crossing two mutants with fragmented mitochondria implies that the mutations are at different loci, restoring the normal morphology in the progeny.

Step-by-step explanation:

The progeny having tubular mitochondria after crossing two mutants with fragmented mitochondria suggests that the mutations are likely at different loci.

This outcome fits the pattern of Mendelian inheritance, whereby each parent may have had a recessive mutation at a different genetic locus, both of which contribute to mitochondrial morphology. When these mutants are crossed, each provides a functional allele for the locus at which the other is defective, thereby rescuing the tubular mitochondrial phenotype in the progeny.

This concept aligns with the one gene-one enzyme hypothesis, as each mutation would affect a different gene necessary for maintaining mitochondrial integrity.