Hello and welcome to day 6 of BEDA. So far so good right?
On Fridays I’m going to be talking about genetics, it’s a massive field in the world of biology. Therefore, I’m going to try and break it down and keep things light and simple! My apologies to any geneticists out there!
So I’ll start with a simple question, why are my eyes brown, or hazel or blue?
Well eye colour is an inherited gene.
The leading question to that is whats a gene? and what does inherited mean?
A gene is a chunk of DNA, that DNA works as an instruction manual for the body to make you you! So each gene codes for a different thing and there is a gene specifically for your eye colour. Genes are broken into dominant and recessive genes. The dominant ones are more likely to occur and the recessive ones are less likely to occur.
Inherited means that it comes from your parents. The sperm and the egg both carry half the amount of genetic material needed to make a human, when they meet the genetic material combines. This means that your genes are inherited from your parents.
So whats the gene for eye colour?
What makes my eye the colour that it is then?
A person’s eye color results from pigmentation of a structure called the iris, which surrounds the small black hole in the center of the eye (the pupil) and helps control how much light can enter the eye. The color of the iris ranges on a continuum from very light blue to dark brown. The protein produced from the OCA2 gene, known as the P protein, is involved in the maturation of melanosomes, which are cellular structures that produce and store melanin. The P protein therefore plays a crucial role in the amount and quality of melanin that is present in the iris. Several common variations (polymorphisms) in the OCA2 gene reduce the amount of functional P protein that is produced. Less P protein means that less melanin is present in the iris, leading to blue eyes instead of brown in people with a polymorphism in this gene.
What does that have to do with my mother and father?
Each of these two genes comes in two different versions (the dominant and recessive versions we spoke about earlier). The genes come in a brown (dark) and a blue (light) version. Dependent on which your parents have determine which genes are expressed in your eyes. Where brown or dark versions of the gene are more dominant.
It is but these two genes have to work together to produce the darker colour, if any of the 2 genes are in the “off position” which is the blue colour then you can end up with lighter eyes. Shown below:
So can you predict a babys eye colour?
Yes you can but there is always an element of chance:
I hope this didn’t get too confusing! Let me know if you have any questions in the comments!