Only a few hereditary traits are determined by a single gene. These properties appear as clear either/or traits.

Examples of hereditary traits determined by a single gene are the type of an individual's earlobe, freckles and the individual's ability to roll their tongue.

The colour of an individual's eyes is affected by several genes. However, it can be thought that brown-eyedness is dominant and blue-eyedness is a recessive trait.


Which features of a girl’s face are dominant and which are recessive?