Genetics

Genetics is the science of heredity. Its applications pervade our daily lives. Whether it's prenatal diagnosis, agronomy, biology, or forensic science, the precision of genetic methods is appreciated. It is both a science, a scientific theory of biological inheritance, and an investigative tool exportable to all fields of biology in order to undertake the analysis of the most varied phenomena.

Genetics studies the transmission of traits from one generation to the next as well as the passage of genes to traits. The discoveries of sexuality, Mendel's laws, the modalities of fertilisation and gamete formation, and the notions of gene, genotype, and phenotype are also important for the history of genetics in all its dimensions.

One of the most fascinating properties of life is that it reproduces itself every generation from single cells such as zygotes (fertilised eggs). This regeneration has existed since the origin of life, and all organisms currently living on Earth, from the smallest, such as bacteria, to the largest, such as whales, result from millions of regeneration cycles.

The history of genetics begins with the discovery of sexuality and reproduction. In animals and humans, this discovery is very old, dating back beyond antiquity, while in plants it is much more recent, with its demonstration at the end of the 17th century by Rudolf Jakob Camerarius" and its general recognition during the 18th century.

At that time, in plants as in animals, the notions of heredity, fertilisation, and embryo development were confused in the notion of generation in the sense of reproduction of individuals. Naturalists, even philosophers, sought to explain the ability of living organisms to reproduce by giving descendants who, overall, resemble them. They were interested at the same time, in a non-distinct way, in reproduction, in the formation of the embryo in animals, and in the transmission of traits, but with more interest in the first two points. To witness the emergence of a science of heredity, seen as the study of resemblances between parents and their children, it was necessary to wait until a separation was conceived between reproduction, the development of the embryo, and the transmission of traits from generation to generation; this could only really be achieved after the work of "Gregor Mendel", who published in 1865 the results of his experiments on the crosses of pea strains showing variations transmitted from one generation to the next. Mendel not only provided the experimental results of controlled crosses, but he also deduced the existence of discrete "factors" that transmit developmental information from a parent to its offspring.

In 1900, the Dutch botanist "Hugo De Vries" rediscovered the laws established by Mendel and published them in a text entitled ''On the Law of Segregation of Hybrids'', considered as the birth certificate of genetics even if this name was not given to the new discipline until a few years later. Almost simultaneously in the same year, Carl Correns and Erich "Von Tschermak" obtained the same results as "De Vries". It was then extended to animals by "Lucien Cuenot and William Bateson".

At the beginning of the 20th century, it became evident that the information specifying the development of organisms was contained in the chromosomes of the cell nucleus. The accumulation of information elements, begun in the 1920s, led to the conclusion that DNA is the genetic material.