This week I’ve had the pleasure of teaching another new group of first year university students some basics of human genetics.
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As usually happens, the question arises “how did you get into this whole genetics thing?”
I still remember the day I fell in love with DNA. I was a first year student myself, right here at the University of New England.
A few weeks into my first biology course (I hadn’t taken biology in high school) one of the professors came in, and taught us about the structure of DNA, and what it does, and how we can manipulate it. From there I was hooked.
DNA is one of those things that, to the uninitiated, seems so overwhelming complex. Something that controls everything from our eye colour, to our blood type, to the shape of our ears, must be complex right?
But when you look right down at what it’s made of, it’s actually surprisingly simple.
Even now, all these years later, I still find it a little mind-blowing that every living thing, from the tiniest microbe to the most complex plants and animals, shares this same simple genetic code.
All of our DNA, whether you are a human, or a dog, or a banana, is made of exactly the same thing – four simple little building blocks. These building blocks are called nucleotides, and each nucleotide is made of just three parts: a sugar called deoxyribose (which is the D in DNA), a group of phosphate atoms, and a nitrogen-rich molecule that we call a base.
There are four different types of these bases, giving us four different types of nucleotides. As geneticists, we use a short-hand code for the four different types – we call them A, C, G and T.
The only real difference between our DNA as humans, and the DNA of any other living thing, is how many As and Cs and Gs and Ts we use, and the order in which we put them.
If we take about six billion of them, and put them into one particular order, we get human DNA.
If we take around the same number of nucleotides, but mix up the order a little, we’ll get the DNA of a bonobo, a type of ape. If we take about half that number of nucleotides, and change the order again, we can have the DNA sequence of an oak tree.
Even now, all these years later, I still find it a little mind-blowing that every living thing, from the tiniest microbe to the most complex plants and animals, shares this same simple genetic code.
Although the basic code itself is so simple, the way we use this DNA is infinitely complex.
In any of our cells, at any given time, we only use a portion of this DNA to make proteins and enzymes that the cell needs to function.
This is why, even though they all have the same DNA, the cells of our body look and work so differently. The cells of our brain, our neurons, contain the same DNA as the cells of our hearts. The difference between them is the way that they use that DNA.
DNA is stunningly simple, yet at the same time so amazingly complex. And that’s why I love it.
Read more Science Matters from Dr Mary McMillan:
