HG Helix Foundational DNA


Introduction - Basic Function and Location

Molecular Structure

The DNA molecule is unique to every organism on the planet and contains an enormous amount of molecular information. DNA is a polymer molecule, meaning it is made up of repeating units over and over again. The basic repeating unit of DNA is called a nucleotide and is made up of three components: a 5-carbon sugar called 2-deoxyribose, one of four nitrogenous bases, and a phosphate group. It is the order of the nitrogenous bases along the length of the DNA molecule that serves as molecular information. Organisms vary in the number of nucleotides found in their DNA, but the number of nucleotides in DNA does not necessary correspond with the complexity of the organism.

As the nitrogen base order within the DNA molecule is the primary way in which information is carried in the DNA molecule, it is worth noting that this part of the molecule comes in four types: Adenine, Guanine, Cytosine and Thymine. Each of these is made of similar components, primarily carbon, nitrogen and hydrogen. The atomic structure of these components provide two different ring structures, two of the nitrogenous bases are structured as a single ring of atoms (pyrimidines) while the other two are structured as two rings of atoms attached together (purines). The shape of the nitrogenous bases is important because it determines which two of the nitrogenous bases can chemically bond together.

DNA is double stranded, meaning that two long polymers of nucleotides chemically bond together to form one molecule of DNA. It is the shape of the nitrogenous bases within the nucleotides that allow the two polymers to bond. The specific nitrogenous bases are selective in their binding to each other in this way. Adenine will typically only bind with thymine, while guanine will typically only bind with cytosine. Although the DNA molecule is held together by the chemical bonds between the nitrogenous bases while inside the cell, those chemical bonds are relatively weak and can be broken easily by excessive heat, radiation, changes in pH and many other factors. This is both useful to the organism when needing to copy or repair the molecule, but also dangerous if the molecule is unintentionally exposed to these conditions.