Gene and genome

Even before the discovery of DNA, genes were known to contain the information for certain traits (such as blue eyes in human beings or the rugose nature of peas), lined up on the chromosomes like pearls on a string.

The word gene was first coined by the Danish scientist Wilhelm L. Johannsen in 1909 to describe the hypothetical "hereditary factors" discovered by Gregor Mendel. In this way, he sought to describe the process by which parental traits are transferred from parents to their offspring and recombined in successive generations.

In the 1940s, this gave rise to the "one gene-one enzyme" hypothesis, according to which genes determined which proteins were produced in each cell. This hypothesis was supported by the discovery of the genetic code during the 1960s, when molecular biology had its heyday. Then in the 1970s, however, it was found that one and the same DNA segment in higher organisms can contain the blueprints for a whole variety of proteins.

Genetic structure exceedingly complex

It was also found that the genes of higher organisms are broken up and that many non-coding DNA sections are strung together with regulatory sections. The genetic structure of higher organisms is consequently exceedingly complex. For this reason, today's definition of a gene also includes those regulatory DNA sequences which decide when protein-coding gene sections are activated and deactivated, as well as the quantities in which a protein is produced in a cell.

The complexity of genes is one of the reasons why it is still not known exactly how many genes make up a human being, although the DNA sequence has almost been completely decoded. The complete genetic information describing an organism is subsumed under the term genome.