Hereditary traits carried by genes that are more likely to be expressed than those of other genes. A dominant trait expresses itself regardless of the function of its corresponding gene. For example, a person who inherits the genes for brown eyes and blue eyes will have brown eyes because that is the dominant trait. An individual needs only one copy of the dominant gene to be affected. This means that if one parent carries the trait, offspring have a 50 percent chance of inheriting it. A dominant gene may be inherited, or it may occur due to a spontaneous mutation that causes dominance of a particular gene.