DNA – What is exactly DNA and how does it work?

You probably now that DNA contains information, but what is it exactly? What is its physical form? In this post I will try to clarify what DNA is and how it works on a simple level.

First of all, a small flashback. DNA is a type of nucleic acid, which is one of the main four categories of organic compounds together with proteins, carbohydrates (sugars) and lipids. In fact DNA is a short version of deoxyribonucleic acid, but do not worry, you do not have to remember that name (except if you are a nerd like me).

DNA is composed of mainly five types of atoms: carbon, hydrogen, oxygen, nitrogen and phosphorus, which are the most common atoms in organic compounds. Each nucleic acid or nucleotide has three parts (Figure 1): a phosphate part, a carbohydrate or sugar part and a nitrogenous base.

_{Figure 1. Nucleotide.}

The first two are the same in all nucleotides, but there are four types of nitrogenous bases, adenine (A), thymine (T), guanine (G) and cytosine (C), which only differ in a few atoms (Figure 2). And in this 4 types of molecule is based ALL life. Repeat that slowly for yourself as many times as required to understand how impressive is this, ALL LIFE. Every. Single. Living. Organism.

_{Figure 2. Nitrogenous bases.}

Now, enough chemistry. You know what it is, but how does it work?
The DNA is a chain of nucleotides linked together, hence containing a sequence of A, T, C and G, in the shape of the famous double helix (Figure 3). DNA is found inside every cell in your body.

_{Figure 3. DNA double helix.}

We say it is double because all information is duplicated. How? Every nucleotide containing A is paired with one containing T, while those with G always pair with those with a C. Hence, every DNA molecule has actually two chains, each containing the same information, but run in opposite directions, hence are antiparallel (Figure 4).

At this point you are probably thinking: this is all very nice but how does actually an organism translate that information into…stuff? Great, that is the Question. Well, DNA is organized in triplets of nucleotides, each one encoding for an amino acid (Figure 4) - STOP! What is an amino acid? So many names man! I know, bear with me, we are almost there. Amino acids are just the building blocks of proteins, that is all you need to know today.

_{Figure 4. Double DNA chain, each one opposite nucleotide composition but encoding the same information. Each triplet of nucleotides can be translated.}

Therefore, DNA encodes for proteins. Exclusively. If DNA is the software, proteins are the robots run by this software. Your DNA creates proteins that are used to obtain everything else that is needed for your body. In fact, DNA creates proteins that can read the DNA to create more proteins! Yes, I know, AMAZING. Here below you can see a protein translating DNA into more proteins.

Finally, DNA is organized in what are called genes. A gene is the sequence of DNA encoding for a single protein. At least that was the first definition, now we know that not all DNA encodes for proteins, some of it has only regulatory purposes, structural function or, most of it, unknown. Nowadays a gene can be defined more as a unit of information.

Now, take a minute to think about those TV ads selling you cosmetic creams for you skin containing snail DNA. The DNA of the snail is the SAME as yours, a plant, a mosquito, Bruce Willis, a virus and a dinosaur, it is the order of the nucleotides that changes, hence resulting in different information. You can apply DNA of snail to your face if you want, it will have the same effect as applying the DNA of the deadliest existing virus, nothing.

Hope you enjoyed! Of course, this was a very simplified and short explanation. If you have any questions feel free to ask and I will try to answer in the comments. Next post will be about GMO