– Ed

How a child looks depends on the genetic material each parent contributes to the child, but the parents’ genes can mix and match in many different ways. The influences from each parent aren’t known until — surprise — after the child is born! Eye colour often is the genetic trait that fascinates parents the most as a child develops. Will the child’s eyes be black, brown, blue, grey, green, hazel or some combination of colours? Early in life, eye colour can change.

What colour will your baby’s eyes be?

Children can have completely different eye colours than either of their parents. However, if both parents have brown eyes, it’s most likely that their children also will have brown eyes. The darker colours tend to dominate, so brown tends to win over the green, and green tends to win over blue. However, a scenario where one parent has brown eyes and the other has blue eyes doesn’t automatically produce a brown-eyed child.

How eye colour is inherited is far more complicated than what was once thought. Generally, it’s far more likely for two brown-eyed parents to have a blue-eyed child than for two blue-eyed parents to have a brown-eyed child. This is because the less dominant blue-eyed trait can be passed along by brown-eyed people until the genes for the lighter eye colour happen to match up, possibly many generations later. Two blue-eyed parents, on the other hand, are much less likely to have children with dark eyes. This is because the genetic trait for darker eyes is so dominant it would be highly unlikely that two blue-eyed individuals would both carry the trait to be expressed in their kids’ eyes. Still, due to the complexities of how genetic traits are passed along, it’s not impossible for two blue-eyed parents to have a brown-eyed child.

How eye colour develops

The coloured part of the eye is called the iris, which has pigmentation that determines our eye colour. Human eye colour originates with three genes, two of which are well understood. These genes account for the most common colours, namely green, brown, and blue. Other colours, such as grey, hazel and multiple combinations are not fully understood or explainable yet.

At one time, brown eye colour was considered “dominant” and blue eye colour was considered a “recessive” trait. But modern science has shown that eye colour is not at all that simple. Eye colours aren’t just a blend of the parents’ eye colours, as in mixing paint. Each parent has two pairs of genes on each chromosome (paired strands of DNA that contain genes or inherited traits), and multiple possibilities exist for how this genetic information is expressed in terms of eye colour.

Changes in eye colour

Most Caucasian babies are born with blue eyes that can darken in their first three years of life. Darkening occurs if melanin, a brown pigment usually not present at birth, develops with age.

The iris is a muscle that expands and contracts to control pupil size. The pupil enlarges in dimmer lighting and grows smaller in brighter light. The pupil also contracts when you focus on near objects. When the pupil size changes, the pigments in the iris compress or spread apart, changing the eye colour a bit. Certain emotions can change both pupil size and iris colour. That’s why some people say their eyes change colours when they’re angry or loving. Eye colour also can change with age. This happens in ten to fifteen percent of the Caucasian population (people who generally have lighter eye colours).

Share this on Facebook: