X-inactivation

I absolutely abhor 'genes and society', a module I took during special semester. But I did learn one interesting thing that I will always remember and thats x-inactivation.

X-inactivation is a process by which one of the two copies of the X-chromosome present in females is inactivated. It has to be inactivated or else females will have alot of health problems. Its the reverse for males though. It can never ever be inactivated because they have only one X chromosome.

Have u ever seen a tortoise shell cat with patches of various colours like the one above? Its because the colour of the fur alleles lie on the x-chromosome and so the orange patches might result from the father's x-chromosome while the black patches might result from the mother's x-chromosome. A similar thing happens in humans too.

And so I looked at my hand, and wonder whether its the paternal X-chromosome or the maternal X-chromosme that codes for that particular patch of skin., but of course, I can’t tell as it all looks the same. I always thought the genes somehow merge and ta-daaaa! it becomes my very own gene and my own unique skin. But apparently not, some parts of my skin code for my father's skin and some parts of skin codes for my mother's skin. My skin is mosaic.

Somehow, I can never look at a tortoise-shell cat now in the same way as I did before. I often stop in my tracks when I see such a cat and stop to wonder which spots of colour belonged to its father and which spots of colours belong to its mother. I look at the cat and it looks warily back at me, seemingly increasingly alarmed at the amount of attention I am paying to it. As I walked closer to take a closer look and marvel at this physical manifestation of x-inactivation happening right in front of my eyes, the cat starts to flee away from me. Sigh…