You can think of genes like your own exercise habits. Genes can be on or off - or anywhere in between.
Basically, genes can become more or less active. It is important to remember that genes are not just on or off. Or maybe the gene became more active and started to make more pigment protein later in life. All or nothing?īut what about changes later in life such as in the case of the boy that you ask about? The boy you mentioned may have had an eye color change later in life because for some reason the start up of the eye color gene was delayed. Usually by their first birthday, a baby's eye color has settled in (although it can sometimes take three years or even longer). That is why so many babies have blue eyes for their first months of life. But it can take a while for the cell to ramp up to the final levels of pigment. Light then triggers the eye cells to start reading the eye color genes. This means that a lot of babies start off with blue eyes. And for eye color, an unread recipe means blue eyes.Īt birth, the genes that make the pigment protein are not being read by the cell (they are turned off). An unread gene is just a piece of DNA - an unused recipe. If the cell doesn't read the gene then you don't get a protein (no "spaghetti"). If no one reads the recipe, gets the ingredients and follows the directions, what do you have? A piece of paper. Think about a recipe for making spaghetti. Remember genes are like recipes for making proteins. Let's say you have the gene(s) that lead to lots of pigment in the stroma of the iris. The same phenomenon that makes the sky blue is also what makes people with little or no pigment in their stroma have blue eyes. People with very little pigment have blue eyes, some pigment gives green eyes and lots of pigment gives brown eyes. As you can see from the picture below, the more pigment you have the darker your eye color. The genes for eye color determine how much pigment is in a part of the eye called the stroma of the iris. So what is going on here? How can you get the genes for brown eyes but not have the brown appear until later in life? It has to do with how genes work. And eye color can and does change for some adults. Children's hair will often darken with age. Many babies born with blue eyes end up with green or brown eyes.
People tend to think of traits like eye color as rock steady.
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