We've all heard the word and we've been told how amazing it is, but what exactly is DNA, and what does knowing more about it do for us? Knowledge of DNA, what it is, and how it works, is one of the most important pieces of knowledge that the human race has. As we unlock more and more of its mysteries, we are starting to realize the implications of its mastery. We're not talking about solving more cases on CSI here either, we are on the threshold of much, much more. Genetic disorders better watch out, because we're coming for them.
The easiest way to look at DNA is to start big and then we can zoom into this book of life. We start out as a single cell called a zygote. Inside of this cell there are 23 chromosome pairs. These chromosome pairs are a fusion of DNA that came from each parent. When they came together and created you, they created this zygote cell with 3 billion base pairs of DNA. These base pairs are essentially the recipe for how to build you. It will also help to picture it as a book with so many pages that it would make Stephen King jealous. We will come back to that metaphor later.
What are these base pairs? They are chemicals that we ascribe names to and which are most popularly displayed as the letters A C T G. A stands for adenine, C is for cytosine, G is for guanine, and T is for thymine. Life really is chemistry. One of the many fascinating things about these chemicals is that they only bond with their partner chemical, they are monogamous if you will. A bonds with T and G bonds with C and that's it, they will not bond with the other two chemicals or themselves. When you see the well known pictures, like the one to the right, you are looking at the double helix. Those rugs in the middle of that twisted latter are these chemical pairings. They are attached to a DNA molecule comprised of sugar and phosphate.
Now back to DNA as a book. Inside of this book there are 64 different words. All of these words are three letters long. The word CGA, for instance, is the recipe for creating the amino acid arginine in the cell. That is the basic language of DNA. We still have plenty to learn before we can understand everything this book says. We know how to read the word for a grain of sugar and a pinch of flour. What we have a hard time with, is how much to add, what else needs to be added, and in what order they need to be added together, so that we bake a marble cake and not cornbread. We also rarely know when the recipe we are reading is no longer the instructions for baking a cake and is now onto the instructions for how to make a hamburger.
Sometimes we do know, however. We know where the genetic markers are on your chromosomes for certain diseases and disorders, and soon we will know more. In the case of Huntington's, a horrible disease that steals a person's intellectual capacity slowly over the course of years and even decades, we know exactly where to look to determine if a person will develop this disease. We do this by looking at a certain place in a person's genome and seeing how many times the word CAG appears in a row. CAG is the recipe for creating glutamine. If the word is repeated 35 times or less, a person will not develop the disease. More repeats spell doom because it will cause neuronal cells to produce more glutamine than they can handle. By looking at the number of times CAG is repeated, we can tell at what age the disease will manifest itself because we can decipher when the tipping point of overproduction will be reached. Not all word repeats are this fatalistic, in fact, very few are. In relation to disease, most of these word repeats simply put you at a higher risk than the average person.
So what is the good news? For one, knowing the problem means we can work towards a solution. In order to solve 23 + me = x, you need to know what “me” is. The next step is to develop a way to erase these words from every cell in your body where these words cause a problem, like erasing the excess Huntington's word, CAG, from all of your brain cells. You don't have to worry about your foot cells, because even though those words are in the cells of your foot, they are not assigned to that workstation. Their genetic instruction is to activate the production of glutamine in the brain's neuronal cells only, even though the same code is present throughout the cells of the body. .
Recently we have discovered a way to change the genetic code in bacteria and erase some of these bad words using a type of biological search and replace technology. Now the hard work continues as we push forward and learn how to make changes to the trillions of cells in the human organism while doing no other harm. There are an awful lot of brilliant people working hard for us. In time, this work will lead to the defeat of Huntington's disease, and then others victories will follow.