Question: Why is it that my mum has blue eyes and my dad has green eyes, so why is it that both me and my brother have blue eyes? Is green eyes a recessive gene?

Lilian Hunt answered on 10 Mar 2014:

Eye colour is the result of genetics and is a bit more complicated then we first thought as multiple genes seem to affect it. However with your family a possible option could be this:

First things first, you have to know that everyone has two copies of each gene. Sometimes they are exactly the same, sometimes they are different. In addition, sometimes one version will be dominant and will result in eye colour by overshadowing the other recessive version. So if we say that your mum has two copies of the blue version of the eye colour gene and you dad has one green copy and one blue copy, we can say that green is dominant and blue is recessive.

So your mum has ‘bb’ which means she has blue eyes, and your dad has ‘Gb’ which means he has green eyes. That means that you could inherit one copy from each and have either ‘Gb’ or ‘bb’. The chances of each are 50/50. The same can be said for your brother, and just because you’ve got blue eyes doesn’t mean he will have green eyes, he has the same chances of both and what you get doesn’t affect him. It’s a little easier to explain with an image like this: (just imagine the brown colour is actually green!)