[Various topics in population genetics].

Through quite simple mathematic tools, population genetics affords quite simple views in biology or medicine as well as the opportunity to enlarge these views toward topics like epidemiology and public health. It is quite easy to show that every population owns, in its gene pool, a set of deleterious mutations that is maintained because it escapes the natural selection. It may also be pointed out the efficiency of consanguinity in exacerbating the frequency of genetic recessive disease, a newly arisen question in some subpopulotions in Europe. As the medicine is more and more efficient, the dysgenic effect of medicine, due to the transmission of deleterious mutations, may be estimated and we may conclude that it is not as high as some would like to exclaim. The selection has a special effect upon genes located on the X chromosome, especially for the one which is responsible for the Fabry disease.