GENETICS BEHIND SKIN COLOR

In today’s scenario I think its very important to know the genetics behind skin colour. Why? Well this question can be answered by certain other ones “Why is everyone obsessed with fair skin? Why are people running after fairness products?

Skin is an organ which is a part of primary defense system of our body. Until that works fine I don’t think we should be worried about its colour. Lets start with the genetics behind skin color. Like everything in our body skin colour too is controlled by our genes. So unless a fairness cream is a genetic tool that can genetically modify our DNA, they cannot change our skin colour. And it is a fact. No amount of advertisements and arguments can change it.

 

GENETICS BEHIND SKIN COLOUR

Human skin colour is an example of multiple gene inheritance or polygenic inheritance.It is also a classic example of quantitative variation. If you consider 3 dominant genes A,B,C that code for dark pigmentation because more melanin pigment is produced and recessive genes a, b, c for recessive genes as they produce less amount of pigment. Then it is the cumulative interaction between these genes that determines a persons skin colour. For example, AABBCC has the darkest colour as it has all dominant genes therefore more amount of pigment will be produced. Whereas a person with genotype aabbcc will have the lightest skin colour. Different combinations can create different ranges of skin colour. A person with genotype AaBbCc will have an moderate melanin production therefore an intermediate skin colour called mulatto.

Also, other factors such as sunlight, temperature do effect our skin pigment production. That is why people living near the equator are darker that those further away.

BIOLOGY OF SKIN PIGMENTATION

Visual appearance of skin is determined by four major pigments

1. oxygenated and reduced heamoglobin of blood vessels( red and blue in colour)
2. the carotenoids(yellow)
3. melanin (brown pigment, eumelanin)

Apart from these pigment the incident light scattering also plays a role.While all these pigment play a role in skin colour , variations in skin colour is primarily due to the amount of melanin present.Melanin is produced by specialized cells called melanocytes present in the epidermis. The neural origin of melanocytes is reflected in their retention of dendritic processes, which are inserted in the neighbouring epidermal cells called keratinocytes. Keratinocytes produce fibrous protein called keratin and also form the outer dead layer of human skin. Therefore each melanocyte is a one celled secretory gland which supplies  melanin to 36 keratinocytes approximately.

Melanocytes produced within specialized oraganelles called melanosomes in melanocytes . In the preliminary phase melanosomes are filled with fiborous protein matrix. A set of biochemical reaction causes the melanin to be filled in the protein matrix of melanosomes.

Once the protein matrix is filled with melanin, the melanosomes migrate to the dendritic process of the melanocyte. From there, an adjacent keratinocyte engulfs the dendrite. The dendritic wall disappears, and the melanin granules enter the keratinocyte cytoplasm, either singly or in clumps of two or more. Whether the melanin granules are incorporated singly or in aggregates seems to depend on their size.

MC1R GENE

MC1R gene provides instruction to make a protein called melanocortin 1 receptor. This receptor is present on the surface of melanocytes and plays an important role in pigmentation. melanocyytes can make two types of melanin,

eumelanin that is responsible for dark skin colour and black or brown hair

and pheomelanin that is responsible for light skin colour and red or blonde hair

So, it is eumelenin that is responsible for pigmentation.The melanocortin 1 receptor controls which type of melanin is produced by melanocytes. When the receptor is activated, it triggers a series of chemical reactions inside melanocytes that stimulate these cells to make eumelanin. If the receptor is not activated or is blocked, melanocytes make pheomelanin instead of eumelanin.

Skin colour is determined by a number of genes and a number of external factors. The genetics behind skin colour is very simple so is to understand the fact that skin colour is not important.

Now that we know the facts, let me tell you that skin colour doesn’t paint your personality.It does not define you. The function of your skin is to protect you and not define you. Beauty doesn’t lie in lack of melanin or in its presence.It lies in your personalty. No amount of fairness cream can change your genotype. Love yourself , you are beautiful the way you are.