Every human rich or poor is a proud owner of a huge book of Gene. It’s unique to him and decides whether that gentleman will be dark or fair, tall or short, healthy or sick.
Our Gene is a very long, linear molecule, a coded version of how to make another copy of us.
It’s our blueprint. Surprisingly the whole code for a complete human being is written down with only four alphabets: A, C, G and T. And it’s the sequence of those subunits that defines that blueprint.
A single strand of our genome is around 3.2 billion nucleotides in length. And the whole thing is over six billion nucleotides long.
If you take all the DNA out of one cell in your body, and stretch it end to end, it’s around two meters long.
If you take all the DNA out of every cell in your body, and you stretch it end to end, it would reach from here to the moon and back, thousands of times.
That’s a lot of information.
Yet, one single spelling mistake in these six billion words can spell disaster for the owner of the Gene. Doctors call it mutation.
What is Mutation ?
Imagine the longest book you can think of, “The Mahabharata”. Now multiply it by 100. And imagine copying that by hand. And you’re working away day and night,
Although you’re very, very careful, and you’re paying your utmost attention, but, occasionally, when you’re copying this by hand, you’re going to make a little typo, a spelling mistake — substitute an A for a T, or a C for a T.
That is equivalent to one mutation. Every time our cell divides a true copy of the whole six billion letters are made and handed over to the new cell. Any mutation on the way is also transmitted to the new cell.
The P53 system that prevents cancer.
Luckily, we have a proof reading system. It is known as the P53 system. It localises any defect in our DNAs, tries to repair it. If not possible it tries to arrest those defective cells.
Actually, when a mutation creeps into the P53 system itself, the DNA defects cannot be fixed. Defective cells go on multipling without stop. We call it cancer.
Dr Ramakanta's Ideas 