Nucleic Acids: DNA and RNA
Relatively recent, in the forties of the previous century, scientists believed that the inheritable information was stored in the proteins of the body. Nucleic acids had just been discovered and were considered too small to be of any importance. But then James Watson and Francis Crick unraveled the structure of those nucleic acids, which lead to the discovery that nucleic acids in fact produced proteins.
Nucleic acids are molecules that contain an enormous abundance of detailed information: all inheritable information. Nucleic acids occur in all known living entities that use and transform energy: plants, animals, bacteria, viruses and fungi. Animals, plants and the rest are all connected through these nucleic acids. While all living beings may look and act differently, the fundamental basis on cellular level is constituted of the same chemical ingredients.
There are two kinds of nucleic acids: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Nucleic acids are made out of strains of nucleotides, which in turn are constructed by a base containing nitrogen, a sugar containing molecules with five carbon atoms and a phosphoric acid. The nitrogen containing bases are molecules that are called purines or pyrimidines.
Purines: adenine and guanine
Pyrimidines: cytosine, thymine (in DNA) and uracil (in RNA)
DNA contains two strains of nucleotides, that are arranged in the form of a double helix. The bases in DNA are adenine (A), guanine (G), cytosine (C) and thymine (T) and the sugar is 2-deoxyribose. Adenine is always connected with thymine (A-T) and guanine with cytosine (G-C). These bases are bound together by hydrogen bonds that form the steps of the twisted ‘ladder’. The sides of the structure are constituted by the sugar and phosphate molecules.
Certain areas of nitrogen containing bases along the DNA strain form a gene. A gene is a unit containing genetic information or codes for a certain product. And that information is carried across generations. Every cell in an organism contains DNA, because it codes for the proteins that are being produced. The basis of life can thus be found in each cell. When a new cell is produced, the genetic material is duplicated, so that the new cell can start making proteins and transfer the genetic material the next generation of cells.
The order of bases in a strain of DNA determines which amino acid will be produced and the order in which the amino acids are linked together, determines which protein will be made. This, in turn, determines which molecule can be produced or which function can be performed. Every cellular process and every aspect of the metabolism is based on genetic information and the production of the right proteins.
RNA is constituted by the bases adenine, guanine, cytosine and uracil and the sugar used is ribose. In most organisms RNA is not the most important carrier of genetic information. However, many viruses (like the hiv virus) do contain RNA as genetic material. In others, several forms of RNA cooperate with DNA to produce and deliver the proteins that are needed.