Final answer:
To determine if a trait is due to cytoplasmic inheritance or genetic maternal effect, observe the inheritance patterns through genetic crosses. Traits from mitochondrial DNA are inherited maternally, while genetic maternal effects depend on maternal genotype and prenatal influences.
Step-by-step explanation:
To determine whether a particular trait is due to cytoplasmic inheritance or genetic maternal effect, you can investigate inheritance patterns by performing genetic crosses and observing the phenotypic ratios. If a trait is consistently observed in offspring regardless of the father's contribution, it suggests a maternal inheritance pattern, where the trait could be encoded by mitochondrial DNA exclusively inherited from the mother. Conversely, if the phenotype of the offspring depends on the genotype of the mother, but the genes responsible for the trait are contained within the nucleus and inherited from both parents, this suggests a genetic maternal effect.
For example, since mitochondria and, therefore, mitochondrial DNA are inherited only from the mother, traits expressed by mitochondrial genes, such as certain metabolic diseases, will be passed down exclusively through the maternal line. This is a case of cytoplasmic or mitochondrial inheritance. On the other hand, a genetic maternal effect implies that the mother's genotype determines the phenotype of her offspring, regardless of the offspring's genotype, due to factors affecting the egg during its development or other pre-natal maternal influences, as seen in environmental epigenetic effects.