The genetic code: From gene to protein

Composition of genes

The bases adenine, thymine, guanine and cytosine are a sort of letters of the genetic code. They form “words“, which consists of three letters, known as base triplets. In their sequence, information is stored which enables to build up a molecule that is required by the organism. Normally, these are proteins. Proteins consist of long chains of amino acids. Each base triplet encodes one of these amino acids. Thus, the sequence of the base triplets of a gene is the “construction manual“ for the sequence of amino acids in a protein and for the structure of the protein accordingly. The proteins can fulfil various functions. Some proteins are (future) components of cells and work as building blocks for the composition of the organism. Other proteins control the processes in the cell as enzymes. In addition, some of the cells generate proteins which are released into the body as hormones (e.g. insulin), digestive enzymes, etc., where they fulfil their function.


The conversion of the genetic information from the gene to the finished protein takes place in several steps. First, the base sequence is transferred to an RNA strand. This process is called transcription. In the copying process, only one strand is produced and not a double strand with opposite bases, as it is usual for DNA. The RNA strand is still processed in the cell nucleus. Thereby parts that do not carry any information are removed, in addition strands are cut into several pieces for some extent, from which several proteins emerge. Besides, the RNA is provided with protective structures at the ends that increase the stability of the RNA strand and support the transport of the finished RNA from the cell nucleus. The finished RNA is called mRNA (“messenger RNA”).


After the mRNA is transported from the cell nucleus into the cytoplasm, it is translated into proteins in the cytoplasm of the cell. The mRNA attaches itself to structures in the cytoplasm known as ribosomes. The ribosomes move along the mRNA and translate the base triplets (codons) piece by piece into the respective amino acid sequence of the protein to be produced. The proteins then contribute as building blocks of the organism and as enzymes – often in interaction with environmental conditions – to the individual (feature) characteristics of the living creature. Only a single gene determines a few characteristics. Normally, especially in higher organisms, features are a subject to the influence of several genes. The basics of the individual features are passed on to the daughter cells during cell division and from one generation to the next during reproduction.