VIII.1 The detection and study of monomorphic genes became possible only with modern molecular genetic methods
Genes were previously seen as hypothetical factors determining the value of the individual biological traits, the properties of living organisms.In order for the existence of such a gene to be distinguished, the relevant trait for which the particular gene was responsible had to assume at least two values.Monomorphic genes, i.e. the genes occurring in the population in a single variant, could thus not, in principle, be distinguished and described or studied.
Only with the ascendance of molecular biology and following revelation of the material nature of genes, i.e. DNA sections coding proteins or RNA molecules, did it begin to become possible to identify the individual genes without first knowing their phenotype manifestations.This permitted identification of monomorphic genes.Modern methods of molecular genetics, specifically the methods of reverse genetics, permit determination of the biological function of a gene even when only a single variant is known.It is possible to either transfer the relevant gene to the genome of a suitable recipient (through a cell of the germinal line) and thus prepare a transgenic organism or, on the other hand, to employ the gene targeting (knockout) method to inactivate the particular gene in the zygote.Study of the phenotype of these genetically modified organisms then assists in determining which traits a particular gene determines.