By Sanjana Kang-Mullen
Epigenetics is a subfield of biology that allows us to question what is really meant by the phrase, Nature vs Nurture. This fundamental phrase has been terrorising mankind for centuries and allows us to question what makes us so curious about where we are from, what can affect us and do we really get everything from our parents?
Our development is like a recipe, with careful interactions between lots of ingredients. But what happens when we have to work with ingredients that we have never been exposed to before? What do we do when we can’t get the ingredients we need? Well the eternal words of Bear Grylls come to mind…
To better understand epigenetics, I would like to use a banana bread loaf recipe to explain the complex interactions that occur between our DNA and the environment.
The DNA molecule, found in the nucleus of all our cells, is our banana bread loaf recipe. It’s the original recipe of how to make a human and we received this recipe from our parents which they got from theirs and so on and so forth. In this case, we must declare that this family really, really likes banana bread, so it’s been passed down very efficiently.
The DNA is the method of the recipe. When we read the words, we are given information. That information is known as our genes. These genes tell cells how to carry out the functions needed to survive. The genes are thus instructions that tell the baker how to make the banana bread. Without them we wouldn’t be able to carry out what is written on the page. Without the genes, the banana bread cannot become a piece of reality.
Now comes the epigenetic factors. These factors make the recipe analogy a little more complicated. For reasons that scientists are still researching, the sway that epigenetics has over how the recipe for the banana loaf turns out is staggering.
A way to picture this is like so…
The primary recipe for the banana loaf contains all of the ingredients required to make it. Bananas, sugar, flour, eggs, etc. When this is made, the loaf is exactly how it’s supposed to be. The right ingredients are used, it is baked for the right amount of time, in the right shaped tin and so forth. This recipe is the DNA that the first member in the family line possessed.
Imagine now that this first family member has children, their children’s DNA is a mix of their parent’s DNA. Half from Mum, half from Dad. The original DNA has been ‘mixed’ with another set of DNA.
Going back to the recipe, the Mum has introduced her own family’s banana bread loaf recipe. Now the two recipes are to be combined. All of the ingredients are the same, but Mum’s recipe has a note that has been tagged onto the banana bread recipe page. In terms of what occurs with the DNA, the note refers to a chemical group (methyl group) that has been tagged onto the molecule. That is what the image below shows, the black tags are methyl groups that are attached to the DNA. One of these tags within our banana bread analogy refers to the note attached to the Mum’s recipe. This is the tag that says “add cinnamon”.
(Credit: Bogo Biology/Youtube)
You may think, why is that?
Well, here’s why…
The original recipe that both Mum and Dad have, has the same ingredients. This is because our DNA encodes for all humans. Much of what Mum and Dad have in their DNA are extremely similar. What has happened here, via the addition of cinnamon to the recipe, is that Mum’s family grew up in a different area and they had access to lots of spices. When exposed to these spices, they were then added to the recipe. It made the loaf ever so slightly different. Changes to recipes like these is not uncommon. The same goes for DNA. Every recipe we see from families will likely contain notes added due to the environment around them.
As a result, your Mum’s environment has influenced the recipe she has, and the way the banana bread loaf is made. In the same way, her environment will have caused subtle changes to her DNA through epigenetics. In this case, it is the work of environmental changes that have led to the addition of cinnamon, an Epigenetic factor. This never would’ve occurred unless Mum had lived in an area that had constant access to spices.
The addition of cinnamon to the recipe is, in scientific terms, referring to the addition of molecules to the DNA. The DNA itself hasn’t changed at all but there is a note attached to it now. That is what makes Mum different from Dad. That is what makes the banana loaf recipe from Mum’s family, different from Dad’s. However, in reality, these changes occur in much higher abundance, so to explain via the loaf analogy, cinnamon wouldn’t be the only difference in the two recipes. There would be subtle changes in the timings of baking the loaf, the number of bananas used, the size of the eggs added, the addition of cinnamon etc.
Epigenetics, therefore, is responsible for how Epigenetic factors like our molecules from our environment and the varying concentrations of the molecules consumed, impact our gene expression and even the DNA passed onto future generations.
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Deans, Carrie, and Keith A Maggert. “What Do You Mean, ‘Epigenetic’?” Genetics, Genetics Society of America, Apr. 2015, www.ncbi.nlm.nih.gov/pmc/articles/PMC4391566/.
Mazzone, Roberta. “The Emerging Role of Epigenetics in Human Autoimmune Disorders.” Clinical Epigenetics, BMC, 26 Feb. 2019, clinicalepigeneticsjournal.biomedcentral.com/articles/10.1186/s13148-019-0632-2#citeas.
TedTalks. “What Is Epigenetics? - Carlos Guerrero-Bosagna.” Youtube, uploaded by TedTalks, 27 June 2016, www.youtube.com/watch?v=_aAhcNjmvhc.
TedTalks. “Epigenetic Transformation -- You Are What Your Grandparents Ate: Pamela Peeke at TEDxLowerEastSide.” Youtube, uploaded by TedTalks, 10 Jan. 2014, www.youtube.com/watch?v=Udlz7CMLuLQ.