how hazel eye colour and heredity works



I only have a basic understanding of eye colour in the brown/blue recessive and dominant example from high school biology.

My husband and I both have hazel eyes. Our daughters both have dark brown eyes much darker than either of us. How is this possible? I thought the dark brown would be dominant and so my husband or myself would need to have this dark brown gene?

Meanwhile our son has blue eyes.

My own parents have blue eyes and hazel. My husband’s parents have blue and green eyes.

Where is the dark brown coming from?



There are 2 eye pigments—yellow and brown. And the lack of pigment is blue. If you only have yellow pigment, then your eyes will be green as the combination of yellow and blue makes green. If you have yellow and a limited amount of brown, that makes hazel. Brown pigment or brown and yellow make brown eyes. Several different genes control eye color so you have multiple signals for brown and yellow and no color.

So if you and your husband both have hazel eyes. That means you both have some combination of yellow, brown, and no pigment. These genes are transmitted separately to your baby, and the baby only gets half of them. So one baby happened to get more of the genes for brown and less or none of the genes for no color. And your other baby didn’t get any of the genes for brown or yellow eye pigment, so has blue eyes.