A pair of genes that fight just right, and the radio up…

"The capacity to blunder slightly is the real marvel of DNA. Without this special attribute, we would still be anaerobic bacteria and there would be no music." ~ Lewis Thomas


Alright friends, it’s time to get another bio basic under your belt. Let’s talk DNA. It is constantly referenced in everyday life (and in this blog) and it is important to know at least the basics (I took an entire class on DNA – the science world knows a LOT! I’m keeping it basic).

Deoxyribonucleic Acid (DNA) is the basis of life. Every living organism, from single cell bacteria to humans, has the exact same basic structure of DNA. It is a long strand (polymer) of repeating units called nucleotides. A nucleotide has a backbone made up of a phosphate group and a sugar (a 5 carbon sugar called 2-deoxyribose). Hanging off of the sugar is one of four bases: adenine, guanine, cytosine, and thymine. These are the A, G, C, T that you remember hearing about in high school. This basic structure (a phosphate, a sugar and a base) makes up a single nucleotide. The nucleotides are then strung together to make a long chain of nucleotides by having the phosphate of one nucleotide bond with the sugar of another (creating a very strong phosphodiester bond – my favorite type of bond). To stabilize itself, DNA forms a double stranded molecule that twists around itself in a helix. The bases of each nucleotide will form hydrogen bonds with matching bases until there is a double stranded helical structure.


Dig deep and try to remember… A pairs with T and G pairs with C…

The order of these bases is what is important. There are a lot of proteins that are able to read DNA and turn the code created by the bases into proteins that can create living things. Everything you are made of and how you look and function comes from your DNA. The same is true for all living organisms. Ninety-nine percent of all human DNA has the same order of bases. The remaining 1% is what makes each person a little different from the next.

DNA is tiny, but it is super long. It will end up coiling itself up to save space. I mean, it does need to fit inside the nucleus of almost every cell in your body (I won’t go into mitochondrial DNA). In humans, DNA coils up and forms linier structures called chromosomes. We have 22 pairs on non-sex chromosomes (autosomal) and one pair of sex chromosomes (X and Y). The chromosomes come in identical pairs because that is what your body needs to have when it copies the DNA before a cell divides. DNA replication – that’s a whole other post.

When you talk about all the DNA in an organism, you are referring to the organism’s genome. The human genome contains around 3 billion base pairs. There are about 20,000-25,000 genes in the human genome, meaning that only around 2% of the 3 billion base pairs actually code for known things. The rest is random DNA or Junk DNA. Yup, that really is the scientific term for it, Junk DNA. It is not really “junk” and may/probably has a function, but scientists just don’t know what that function is.

DNA has a lot of other fun aspects to it. For instance, bacterial DNA comes in circular, not liner chromosomes. Organisms that live in more extreme environments often have higher G-C base pairings in their DNA. Guanine (G) binds with Cytosine (C) using three hydrogen bonds (compared to Adenine (A) and Thymine (T) using two) making it stronger and harder to break apart. DNA can come in a variety of helix types and has major and minor grooves which serve several functions… I could go on and on…

I think this is a good start to DNA. It should help demystify this crazy little double helix inside of you!