Nucleic acids are polymers that were named because they were first described in the nucleus. There are 2 types, deoxyribonucleic acid and ribonucleic acid (DNA & RNA). DNA is the storage vessel for genetic information and RNA largely plays a role in expressing this genetic information.
The building blocks (monomers) of nucleic acids are called nucleotides, which are made up of individual subunits. Nucleotides consist of a 5-Carbon sugar (a pentose), a charged phosphate and a nitrogenous base (Adenine, Guanine, Thymine, Cytosine or Uracil). Each carbon of the pentose has a position designation from 1 prime through 5 prime. One major difference between DNA and RNA is that DNA contains deoxyribose, and RNA contains ribose. The discriminating feature between these pentoses is at the 2′ position where a hydroxyl group in ribose is substituted with a hydrogen.
DNA is a double helical molecule. Two anti-parallel strands are bound together by hydrogen bonds. Adenine forms 2 H-bonds with Thymine. Guanine forms 3 H-bonds with Cytosine. This AT & GC matching is referred to as complementarity. While the nitrogenous bases are found on the interior of the double helix (like rungs on a ladder), the repeating backbone of pentose sugar and phosphate form the backbone of the molecule. Notice that phosphate has a negative charge. This makes DNA and RNA, overall negatively charged.
The animation shows that there are 10 bases for every complete turn in the double helix of DNA.
Notice how the nitrogenous bases rings are parallel or stacked on top of each other.
