Epigenetics: Can we change our genes? - BBC World Service

For a long time, scientists believed that it  wasn’t possible to alter our genetic code. After all, the genes that make up our DNA  contain all the information about who we are. They give instructions to the body’s cells and  determine everything from the colour of our eyes to the functioning of our lungs and our propensity  for diseases such as cancer or diabetes.

But the life one leads, along with  other factors, makes it more complex. Imagine two identical twin brothers. Their DNA is the same, but the  way they live is very different.

One leads a calm life, the  other has a stressful job. One exercises more, but the other eats better. The twins start to acquire  different characteristics or perhaps develop different diseases.

How can this be if their  genome is exactly the same? The reason is that the human body  has a natural way of turning some of our genes on or off in response to the  environment and the lifestyle we lead. And it does so without modifying the DNA.

It's called epigenetics. And the set of chemicals that mark the genome and  tell cells what to do is known as the epigenome. Think of DNA as an instruction  manual for how the cell should work.

Every cell in your body has one of these manuals. The epigenome is like someone  picking up a pack of coloured markers to emphasise or cross out  different parts of the manual. This part here, it's more important,  accentuate it.

This one, don't use it. And how does it do it? Every cell in your body contains  almost two metres of DNA.

In order for it to fit inside  a cell, the genetic material is wrapped up in a set of proteins called  histones to form a compact structure. But that means the cell doesn't  always have easy access to the genes. This is where epigenetics comes into play.

Epigenetic marks are chemical markers  that act on this structure to give it instructions to compress or decompress the DNA. If they compress it, the cell cannot access  the information and the gene is turned off. Epigenetic marks that decompress the DNA allow  the cell to read the gene and turn it on.

This process starts as soon as the first  cells of the human embryo begin to divide. That is why it is so important  for the baby what its mother eats, her emotional and physical state, plus  the medicines and vitamins she takes. All that information can be transmitted in the form of chemical signals to  the baby through the blood.

If the mother's diet during pregnancy is  poor, the baby could be more prone to obesity, since its epigenome has programmed it to  store more calories every time it eats. This phenomenon has been tested  in several studies with women who went through periods of prolonged  famine during wars, for example. But the role of the father is also  important because he can transmit some of his epigenetic marks to his children.

For example, if a father has been  smoking heavily since adolescence, this may result in a shorter life expectancy  for his children and even for his grandchildren. The epigenome acts on our body throughout  our lives, not just in the embryonic phase. As in the example of the twins, our  habits, our diet, our experiences, and the environment in which we  live can turn our genes on or off.

But it goes further: epigenetics  shows that nature may have found a way to pass on trauma to subsequent generations. In one experiment, scientists made male mice associate the smell of cherry blossom  with pain caused by an electric shock. These mice procreated and their offspring also  became nervous when they were presented with that smell, despite not having had contact  with their parents during their upbringing.

The third generation of mice,  the grandchildren of the first, also showed greater sensitivity to that  smell, more than any of the others. In their DNA, the scientists found epigenetic marks on a gene responsible for coding  a protein that is a receptor for odours. They also had more neurons  in their brains responsible for detecting the smell of cherry blossom.

But that does not mean that we are predestined to relive the emotions of our  parents and grandparents. Scientists are still studying how this type of epigenetic transmission of  trauma can occur in humans. Even so, they already predict that  it might be possible to reprogramme this same mechanism to make us healthier,  since epigenetic changes are reversible.

This opens up a huge universe of  possibilities in the scientific world. For example, there are studies to create  drugs that make it possible to reverse the epigenome markers that favour  the appearance of certain tumours. Epigenetics could also revolutionise the treatment of different diseases such as diabetes,  lupus, Alzheimer's or even some addictions.

The big challenge now is how to develop  drugs that act only on the negative markers, without impacting the positive markers. Epigenetics proves that not everything is written in our genes and that we can  positively influence our epigenome. Something that can not only benefit us in  the present, but also our future generations.