Maternal inheritance of mitochondrial mutant phenotype poky

Reciprocal crosses of poky and wild-type Neurospora produce different results because a different parent contributes the cytoplasm. The female parent contributes most of the cytoplasm of the progeny cells. Brown shading represents cytoplasm with mitochondria containing the poky mutation, and green shading represents cytoplasm with wild-type mitochondria. Note that all the progeny in part a are poky, whereas all the progeny in part b are normal. Hence, both crosses show maternal inheritance. The nuclear gene with the alleles ad⁺ (black) and ad⁻ (red) is used to illustrate the segregation of the nuclear genes in the 1:1 Mendelian ratio expected for this haploid organism.