Nucleic Acids

An important group of polymers are the nucleic acids. Nucleic acids are unbranched polymers whose monomers are called nucleotides. Nucleic acids are made up of a nitrogen base, a phosphate group, and one of two sugars--ribose or deoxyribose . The acids created from these monomers carry genetic information from generation to generation.

The nucleic acid that contains the sugar ribose is ribonucleic acid (RNA).
The nucleic acid that contains the sugar deoxyribose is deoxyribonucleic acid (DNA).

DNA

You probably already know some things about DNA. DNA is a double helix. It has two strands wrapped around each other with hydrogen bonds at specific sites. The two strands are complementary. In other words, each of the strands has all the information necessary to recreate the other half. The structure of DNA resembles a twisted ladder.

DNA is found within every cell of your body and contains the instructions necessary to make an entire organism. Sometimes DNA is referred to as the blueprint of the cell. Just like an architect provides the blueprint for a building, your cells provide the blueprint (DNA) to make you. In order for the DNA to fit inside your cell's nucleus it must be folded into small tangled masses called chromosomes. Each chromosome is contained within a protein wrapping. Humans have a total of 46 chromosomes (23 pairs) found within each body cell. The only exception is the gametes (sex cells), which contain a total of 23 chromosomes each.

To understand how DNA works as a blueprint for protein synthesis, you need to know a little bit about the structure of DNA. DNA is made up of nucleotides. Nucleotides are the building blocks of DNA. Each nucleotide is made up of a sugar, a phosphate and a nitrogen base.

There are four nitrogen bases that make up nucleotides. Each base is represented by a letter and is always paired with the same partner. The four bases and their corresponding letters are as follows:

adenine A	thymine T	guanine G	cytosine C

A always goes with T, and C always goes with G. (You can remember that A and T spell AT; and C and G look alike.) Look at the following base pairs. You can see that in DNA A can only bond with T and C can only bond with G. Click on the start button to see these in motion.