The ABO gene determines what blood type you have. These genes can come in different versions, called alleles. You have two copies of most genes, one from mom and one from dad. Each gene has the instructions for one small part of you. There is a set of recipes to be a muscle, a different set to make skin, a third set to carry a nerve signal and so on.Ī big part of the instructions comes in sections of DNA called genes, which are like individual recipes. In a way, it’s a lot like a recipe book with all the instructions that tell each of your cells what to do and when to do it.
Your DNA has the instructions for making you. As you’ll see it has to do with what a gene actually does. What I thought I’d do for the rest of the answer is talk about what is actually happening in the cell with codominance. So codominance definitely happens in people! There are other examples as well, including blood cell shape in sickle cell disease. People with this blood type have A and B proteins at the same time. The classic example that we’ll go over in more detail is the AB blood type. You are right that codominance happens when two traits are both visible at the same time.
This heterochromia happens for different reasons (click here to learn more). But having two different colored eyes is not one of them. There are definitely codominant traits in people.