What is DNA?

The term DNA is now in just about everyone’s lexicon, as it has been made famous by Jurassic Park and crime lab shows. I’m going to skip some of the technical details and get straight to the interesting stuff.

Before getting in the meat of things, I’d like to first introduce the purpose of DNA. DNA is like a book of commands, these commands are copied and direct the formation of protein. In my opinion, proteins are more difficult to understand. Proteins are not alive, they do not have a brain and are not capable of thought yet they can perform amazingly complex functions. I try to think of proteins like tiny little robots created by our cells to carry out specific tasks. For example, there are two main proteins in our muscles, and they are lined paralell to eachother and overlap a fair amount. When one of these proteins is triggered to move inwards compared to the other (towards the center, increasing the overlap), it causes the muscle to contract. So essentially, muscle contractions are the increase in overlap of these two proteins, while muscle relaxation is simply a decrease in the overlap between these two proteins. When people people train to increase their strength, they are NOT increasing the number of muscle cells, but instead are increasing the number of these proteins in the muscle cells - because the cells have more stuff in them, they become larger. Another interesting set of proteins are digestive enzymes, they are released by different parts of our body to break down food in our digestive tract (stomach and upper small intestine mostly), they are very specific and will only cut the food types that were directed to. Therefore, we have different enzymes for sugars, fats and proteins. People that are lactose intolerant actually lack lactase, the enzyme that breaks down lactose - the sugar present in milk.

Now lets move on to DNA, also known as deoxyribonucleic acid is a molecule made of a phosphate backbone, a sugar ring and nitrogenous base. What’s important to know is the phosphate and sugar are always the same for every DNA molecule, but the nitrogenous base is not! The base is either A, C, T or G (short form for their chemical name). It is a complementary system, meaning that each letter is paired with a letter and it is ALWAYS the same letter. In part because of this complimentary system, DNA forms the well known helical form. The fact that DNA is complementary also means that if one sequence is damaged (mutated), it can be fixed by simply looking at the other sequence, as they have the same information but in reverse. For those interested, A binds T and C binds G. Now, the easiest way to understand how DNA works is to use the analogy of the written word: letters create words and many words create phrases. A, C, T and G are the letters, when you have three letters you have a word and when you have many groupings of words you have a phrase. Here is an example:

AAA CCC TTT GGG, here you have, based on our analogy, four words. We call these codons. Each codon calls for the attachment of an amino acid - the building block of proteins (ie. when digest protein in a meal, it is broken down into amino acids which are later used to form new proteins that our body can use). Depending on how many amino acids you have an what order they are in, you get a different protein. It’s important to note that DNA does not create proteins directly, instead there is an intermediate called RNA. Unlike DNA, RNA is not nearly as finely structured, it’s essentially a single straight line without a helical structure and it is not usually paired. RNA is actually serves as a copy of DNA to be used as a blueprint for protein construction. This allows the body to create many copies of DNA and circulate a large number of RNA blueprints in the cell and create many new proteins simultaneously. If you think about it, if there wasn’t RNA, you could only create one protein (of the type that you want) at a time because the DNA section you need to access can only be read one at a time. Basically, RNA allows the amplification of the DNA sequence, from one to many. RNA is pretty neat, while simpler in structure than DNA, it is still highly complex and can hold a lot of detailed information. It is thought that life originated from RNA and DNA evolved from that. RNA itself is also found in viruses, namely HIV (it’s also referred to as a retrovirus, because it reads and makes copies of itself backwards).