Epigenetics — Why Your Clone May Never Be Like You
Nurture FTW?
Even if you don’t know much about biology, you will probably know about genetics. People are always talking about how their DNA is to blame for their curly hair, skin colour, or predisposition to diabetes. However, even those with in-depth knowledge of biology, seem to lack knowledge of epigenetics. It definitely is a far more recent discovery than genetics and perhaps for that reason, has been largely overlooked.
Let’s start with a pair of identical twins or clones i.e. 2 genetically identical individuals, and let’s put them in two separate wombs. One mother smokes, drinks, eats junk food, lives in an over-polluted city and barely moves from the sofa to the bed each day. The other, grows her own vegetables with no fertilizers, does yoga every morning and lives in a treehouse in Bali. Which child is going to be healthier, stronger, more intelligent even? The answer is quite evident and anyone with “common sense” could confirm that both offspring could differ dramatically.
Epigenetics is the reason for this. Epigenetic modifications are chemical alterations made “onto” the genetic material or the histone proteins around which the DNA is wrapped. These chemical modifications alter the accessibility of the genes and thereby determine whether or not they can be read and processed. Simply put, epigenetics is the grammar in the language of genetics. The epigenome provides the rules for how the genome will be read making it the bridge between one’s environment and genes.
In fact, major biological events in our lives from birth to death are governed more by epigenetic modifications than by our genes themselves. Let me highlight some of these:
Development: Fetal development is a turbulent time in the epigenetic landscape. It involves large scale erasures of epigenetic codes followed by reinstatement of the appropriate patterns. This is the time at which a single cell with no specific properties develops into multiple cell types each of which has clearly defined function. All this occurs in a very timely manner and environmental changes at any of the critical stages in the process could have major impacts on the infant that develops.
Cognition, Learning, Behaviour: Epigenetics has a crucial role to play in the development of most cognitive functions affecting how we think and behave. Enzymes involved in epigenetic modifications affect fear conditioning, stress responses, memory formation and almost everything in between. Thus, every experience and external interaction shapes our mental faculties in a specific way. The reason your clone will never be like you.
Onset/Manifestation of Disease: Epigenetics can be a major determinant in the development of various diseases. For example, gestational diabetes for a woman can mean an increased probability of the development of insulin resistance for her offspring. Several studies have also proven unquestionable links between epigenetic changes and the manifestation of cancers. It is also clear that although a person may have a high genetic risk for a given disease, it may never manifest throughout their lifetime if that mutated/faulty gene is never expressed.
Ageing: Epigenetic changes occur throughout our lifespan and determine how we age. Modifications to chromatin and histones can increase or decrease lifespan/healthspan based on the triggers that cause them. Diet, exercise and sleep cycle are a few of these environmental triggers that directly affect the epigenetic modifications influencing the genome. On the flip side, changes that occur during ageing such as mutations in the genome can, in turn, affect the epigenome.
In summary, all evidence suggests that the epigenome is far more complex and unique to the individual than the genome. Every lifestyle choice we make can create a “butterfly effect” on genetic expression that can affect our biology for multiple generations. Understanding these effects can help us shift from genetic to epigenetic engineering and define more specific cellular competencies to cope with our ever-changing environments.
