What we know about inheritance goes far beyond Mendel’s pea plants. It is not limited to alleles being passed down and predicted through Punnett squares alone, but can also be determined by the environments we live in. This is what epigenetics is all about. The definition of epigenetics is very broad but has many distinctions. While it still examines how genes are passed on across generations, it focuses more on how the environment impacts gene expression instead of homing in on inheritance patterns. This also means that the impacted gene changes can be reversed.
How does it work?
There are three methods in which epigenetics impacts gene expression: how the genetic code is read out and what genes are on and off.
- DNA Methylation– A methyl group (-CH3) is added to the chemical group on the DNA. It is attached to specific spots on DNA, and that specific sequence cannot be read by the polymerases that are responsible for gene expression. The reverse process is known as demethylation, which will turn it back “on”.
- Histone Modification– DNA coils around histone proteins, and should they be packed together, the polymerases cannot read the sequence, effectively turning expression for that gene “off”. If the histones are spread apart, the expression is back “on”. Different groups can attach to either pack or distribute the histone bundles.
- Non-coding RNA– This type of RNA can attach to coding RNA to block the corresponding proteins, and effectively silence the gene expression. It can also attach other groups that could modify the packing of histone proteins to turn the gene “off” or “on”.
What influences epigenetic changes?
Epigenetics can be influenced by many factors, but the most common ones are related to development, age, environment, and health. Before you are born, your DNA will be modified epigenetically so that different tissues can be expressed to develop your organs. This is why all your organs will have the same DNA but appear differently in part due to epigenetics’ role in differentiation. Another essential aspect to consider is age. Your epigenetics will change over time and the number of methylation sites will shift. Finally, another significant influence on epigenetics involves lifestyle decisions and health events.
How do lifestyle decisions and health impact epigenetics?
One way that health impacts epigenetics is through sickness. Germs can change epigenetics, which weakens the immune system. Other epigenetic changes can change the gene expression of a gene like BRCA1, which if decreased, increases the risk of breast cancer. Another condition where epigenetics is impacted is in pregnancy. During the Dutch Famine, children whose mothers were pregnant during the famine were born heavier, and as they grew, these children were vulnerable to having a high risk of conditions such as diabetes, obesity, and schizophrenia.
Aside from these events, other lifestyle decisions can impact epigenetics. For instance, dieting decisions, like having meals rich in polyunsaturated fats, can induce oxidative stress which causes epigenetic changes. On the flip side, diets that have more fruits and vegetables have antioxidants which provide protection against cancer. Other decisions like consuming tobacco and alcohol can act in a cocarcinogenic capacity, inducing epigenetics shifts that increase the risk of cancer. Hypermethylation is also found in a higher presence among individuals who faced stressful and traumatic events early in their lives.
In short, the mechanics of epigenetics involve gene expression beyond inheritance patterns and are in fact directly and indirectly influenced by the decisions we make and the environment we live in. It is important to consider all the factors that contribute to epigenetic changes, as it has not only an impact on your health but also on the generations that follow you.
Author: Maaida Kirmani