In a pedigree, a rare trait appears in both sexes with equal frequency, and each affected offspring has one affected parent. What is the most likely mode of inheritance?

Autosomal dominant inheritance

Explanation:

The most likely mode of inheritance of the trait would be autosomal dominance.

In autosomal dominant inheritance, a dominant allele on a non-sex chromosome is responsible for its transmission across generations. Unlike autosomal recessive traits that require two recessive alleles for their transmission, only one dominant allele is required for autosomal dominant traits and the implication is that it appears in every generation and both males and females have an equal chance of inheriting such traits.

Hence, for a rare trait that appears in both sexes with the same frequency and each affected offspring has one affected parent, the most likely mode of inheritance would be autosomal dominance.