Question

one strain of periwinkle plants has green leaves and another strain has white leaves. both strains are tru-breeding. you do not know if the phenotypic difference is due to alleles of a nuclear or an organellar gene. the two strains were analyzed using reciprocal crosses, and the following results were obtained. a. a plant with green leaves is pollinated by a plant with white leaves: all offspring have green leaves

Answer 1

The reciprocal cross showed that the trait for green leaves is dominant and the trait for white leaves is recessive. We do not know if the trait is determined by nuclear or organellar genes. If the trait is determined by nuclear genes, we would expect a 3:1 ratio of green to white leaves in the offspring of a cross between two heterozygous plants. If the trait is determined by organellar genes, all offspring would have the same phenotype as the maternal parent. However, we cannot determine the type of gene responsible for the trait based on this information alone.