How do dominant genes function in relation to phenotype?

Dominant genes function by determining the phenotype, which is the observable trait or characteristic of an organism. When an individual has at least one dominant allele for a trait, that dominant allele will be expressed in the phenotype, meaning that its associated traits will be visible in the organism. This occurs regardless of whether the second allele is dominant or recessive.

For instance, if a dominant allele is responsible for a trait like brown eyes, an individual with one brown-eyed allele (dominant) and one blue-eyed allele (recessive) will still display brown eyes, demonstrating how dominant genes effectively dictate the appearance of traits in the phenotype. This principle is fundamental in understanding Mendelian genetics and how traits are inherited from one generation to the next.

The other options do not accurately reflect the role of dominant genes in phenotype expression.