A dominant gene is a type of gene that can express its traits even when only one copy is present. This means that if an individual inherits a dominant gene from one parent, the traits associated with that gene will be visible in their physical characteristics, or phenotype. For example, if the gene for brown eyes is dominant, a person with one brown-eyed parent and one blue-eyed parent will likely have brown eyes. In genetics, dominant genes are often represented by uppercase letters, while recessive genes are shown with lowercase letters. The interaction between dominant and recessive genes helps determine various traits in organisms, including humans. Understanding dominant genes is essential in fields like genetics, breeding, and medicine.