Thanks for the great question!

Our genes, which are made of DNA, determine what traits we have, like the color of our hair. A scientist named Mendel discovered that for certain traits there are two different versions of the underlying gene, called alleles. You get one allele your mom and one from your dad. When mom and dad give you the same allele, it will be visible, but when they give you different alleles, one tends to win out and is visible – we call this the dominant allele, and the other invisible allele is recessive. I’ve included a picture called a Punnett Square that illustrates this.

In this picture, each parent has both a dominant (uppercase) and recessive (lowercase) allele of the B gene. If they were to have four kids, then three of four would have an uppercase B, the dominant allele, and this trait would be expressed. One child, however, would have two lowercase b’s, and this child would exhibit the recessive trait.

Dimples are a human trait that are highly heritable, that is, if your parents had them, that means you likely have them. Dimples are the dominant trait, meaning if one parent has them and the other do not, it’s likely their child will have them. So, people have dimples if one of their parents has them. However, as you see in the Punnett Square, it’s possible for two parents with dimples to have a child without dimples, 25% of the time. The science of genetics explains why people have the traits we have.

Thanks again for the great question.