Final answer:
Chuck's most likely genotype for having freckles is Ff, which reflects the inheritance of the dominant freckles allele from his father and the recessive allele from his mother, consistent with the dominant trait inheritance pattern.
Step-by-step explanation:
The question asks about the probable genotype of Chuck, given that freckles are a dominant trait and both Chuck and his sister have freckles, his father has freckles, and his mother does not. Chuck's mother having no freckles implies that her genotype must be ff because freckles are dominant and she exhibits the recessive phenotype. As freckles are dominant, Chuck's father must have at least one allele for freckles. Since Chuck also has freckles, he must have inherited one freckles allele from his father. Therefore, Chuck's genotype could be either Ff or FF. However, because we know that Chuck's sister also has freckles, it's more likely that Chuck's genotype is Ff, as this would allow for the possibility that both siblings inherited an f from their mother and an F from their father.