Yes! Most of us tend to think that the consequences of one’s lifestyle will affect only his/her life. It makes sense until we come to know what we don’t know!
Well, what do we not know?
What you eat, where and how you live, how often you exercise — all of these environmental factors cause chemical modifications around your genes which are then carried over to all your future generations.
Yes, Epigenetics. But before we understand what epigenetics is and how does it do all that magic, we need to understand genetics first.
The human body contains approx 40 trillion cells! The function of all these cells varies depending on where they are put to work. For example, a liver cell performs a different function than the kidney and the brain cell. We function as a whole because of these cells. Cells are the fundamental working unit in our bodies. Cells receive instructions on what exactly they need to do from a molecule called deoxyribonucleic acid (DNA).
The DNA in humans is made up of around 3 billion letters.There are four letters that repeat in a sequence — A, C, T, and G (The four fundamental nucleotide bases: Adenine, Cytosine, Guanine, and Thymine). Humans inherit these 3 billion letters from their mother and 3 billion letters from their father!
The sequence or the order of these letters determines the instruction set for the cells. Within these 3 billion letters there are approximately about 20, 000 genes. The DNA sequence when formed in specific order or pattern, forms a gene that then instructs and helps in the production of essential proteins. These proteins perform all the essential biological functions that keep us alive! Sometimes it takes just one letter in the sequence to be wrong and you might have a devastating disease. This means that the genome sequence is very very very important.
Ok, we know what is genetics now. But that’s not all there is to the story.
Epigenetics is a phenomenon in which modifications happen around the DNA without actually altering the sequence of it. And these modifications are heritable. So, you can transfer things that happened to you in your life span to your children by changing how certain genes are activated or not activated.
To answer this, we need to consider our DNA and how it fits into our cells. So each of the 40 trillion cells contains about 6 feet of DNA molecule. If we were to make it linear and stretch it out, it would be as tall as some NBA player. But then how does it fit into our tiny cells?
In our cells, the DNA wraps around a cluster of 8 protein molecules called the histone. The cells have access to a bit of the DNA molecule before it again wraps around another histone. The histone also has some tails sticking out of it.
Ok! But how is this affecting my genes?
Let’s say you recently started drinking alcohol. You would probably feel the kick after one or two vodka shots. Now you continue drinking frequently for a few months. You find that you do not feel anything even after 4 shots! We all have experienced this. But how does this happen?
This is because your body starts breaking down the alcohol faster. Basically, it switches on a higher expression of the gene that breaks down alcohol.
When you start consuming more alcohol, the liver signals the body that it needs to break down more of the alcohol rapidly. This results in some modifications added to the tails of those proteins (histone) around which the gene that breaks alcohol is wrapped around. These modifications enable the gene to be switched on easily. So they drive up gene expression.
Now after some time, you decide to get sober and control drinking alcohol. The liver does not need to break down a large amount of alcohol anymore so it signals the body again. The modifications that occurred earlier (represented by orange dots on the tails) to drive up the gene expression are replaced with new modifications (red dots) that drive down the gene expression.
let’s say you decide to take it further and stop drinking alcohol completely. The liver does not need to produce enzymes that break alcohol at all. This results in further more modifications at the tails of histones that replaces the previous ones to basically say that turn this particular gene off.
So here, the body has a mechanism to turn genes on or off based on the external factors. But it’s not just binary. There can be some orange dots, some red dots, and some purple dots. So the body shows a wide range of gene expression.
Now if a large number of purple dots (modifications that turn the gene off) accumulate near a cluster of histones, it can result in modifications to the DNA itself that say “I never want this gene to be switched on from now”. In such cases, the histone molecules scrunch together and become so compact that no part of the DNA is exposed for the cell to read. It shuts down the gene expression, almost permanently.
All of these modifications are called Epigenetic modifications! So to summarize, epigenetic modifications are changes that occur on the DNA that modifies the gene expression without altering the DNA sequence.
So how does your lifestyle affect the lives of your grand grand kids? Stay tuned for Part 2.