The chemistry of life and its central dogma

The genetic information flows from the DNA in our genetic material via RNA to proteins, which in turn construct cells with different functions. This principle is called the central dogma of the chemistry of life. It was previously believed that the nucleic acids DNA and RNA serve solely as carriers of the genetic information, whereas proteins in the form of enzymes catalyze the chemical processes of life. The chemist's perspective on genetic information (heredity) and function (biocatalysis) in living cells has changed through the discovery by Sidney Altman and Thomas Cech that the ribonucleic acid RNA can also function as an enzyme.
    RNA molecules consist of long strands of alternating carbohydrate and phosphate molecules. To each carbohydrate is attached one of the four nitrogen-containing bases: Adenine, Cytosine, Guanine and Uracil. These bases constitute the chemical "letters" in the genetic code which determines the compositions of proteins. Each word in this code contains three of these letters, which can be combined in many different ways, e.g., UCA, CGG, ACU. Each word corresponds to one of the twenty different amino acids found in proteins. The cell has developed a sophisticated molecular machinery which can read the words of the genetic code along the RNA strand and join amino acids together in the order required to construct a protein with a specific function.
    The code words in an RNA molecule originate from a DNA molecule. All of our hereditary traits are programmed into the DNA molecules. Most RNA molecules, in contrast, contain information about only one of the cell's many components. For example, one RNA molecule may contain information concerning the pigment in an individual's eyes, while another contains information about insulin. In general, one RNA molecule contains the information from one gene.