There’s so much to know about science and biology that requires background information. This may be tedious to read, but it’s essential to understanding so much of how things work (or don’t, in the case of disease). Many of my posts will provide this kind of background, and they will also be archived in the “Background Info” menu for future reference. If this is old hat to you, that’s okay! If not, please read and learn – it’s worth taking the time so that future posts make more sense.
So probably everyone knows what DNA is. Right? It’s talked about on the news all of the time. Maybe vaguely it’s defined in your head as “the building block of life”. Maybe you know about the double helix (more on that soon!!). Maybe you’ve even isolated DNA as part of a science fair experiment. But really, WHAT IS IT?
I remember the first time I learned what DNA was in a biology class. The biology book’s fourth chapter was entitled “Marcomolecules” and one of these molecules was DNA. It was confusing. All the different macromolecules were introduced all at one time. I had no idea how they were related to one another or why I was learning about them. And why were they called macro? That implied big, and I knew for a fact that DNA was small (because it has to fit in a cell!) So let’s break down what DNA really is, in a way that I hope is far less confusing than my first biology book.
DNA is the genetic code that makes up all of human life – or any life on earth (yes, your DNA is made up of the same parts as angler fish DNA or tulip DNA) . A lot of times, people compare it to a blueprint, where the DNA provides the instructions to make whatever organism it is supposed to create. This is essentially true. DNA itself is made up of individual parts called nucleotides. There are four nucleotides – each containing a different base:
- Adenine (A)
- Thymine (T)
- Guanine (G)
- Cytosine (C)
These are often abbreviated using the single letter listed above – A, T, G or C. These bases are each associated with a sugar and a phosphate, which forms what is commonly referred to as the “backbone” of DNA. Look at the picture above to see what this looks like. DNA looks like a ladder – the sugar and phosphate forms the sides of the ladder (the light blue in the picture) and the bases form the rungs. What’s really neat and interesting is that these bases don’t pair up randomly. Adenine always pairs up the Thymine and Guanine always pairs up the Cytosine. Want to know why? Well, it’s because of the shape of the bases. Take a look at the pictures above. A and T have two places where they can bind to each other and G and C have three. If you tried to get an A to bind to a C, it wouldn’t work because the C would have an empty binding spot hanging out there.
So why in the world is this important at all? Well, think of this – because we know this rule, if we know the sequence of As, Ts, Gs and Cs of one strand of the DNA ladder, we also know sequence of the other strand. This means that when DNA copies itself (what scientists call replication), two copies of the DNA can be made relatively easily: the ladder unzips and each separate side of the ladder functions as a template to make two exact copies of the DNA. This process happens 10,000 trillion times in your lifetime.
There are so many interesting things about DNA and how it works – all will be discussed in future posts. But in case you want more information right now, I have compiled interesting DNA references can be found here.