Population genetics deals with investigation of genetic composition of populations, resp. of mechanisms changing the genetic composition. The genetic (DNA-) properties within the genetics are studied from the aspect of a definite racial group, i.e. population of creatures, methodology is characterised by application of mathematical modelling. It has a key role in the evolutionary biology, as also elementary steps of evolution take place on population level. It also studies the distribution of allele frequencies, i.e. versions of genetic properties, and their changes within the frames of the four main evolutional mechanisms, which are natural selection. genetic drift, mutation and migration (gene flow).