History of genetics

The history of genetics began not so long ago, approximately in the second half of the 19th century, from the research of Austrian monk Gregor Mendel. Before, people did not know what determines the heredity and variability of organisms. Systematic studies have not been conducted in this branch of science. Since antiquity, there were two hypotheses about why offsprings are similar to their ancestors. These are hypotheses of direct and indirect inheritance.

According to the hypothesis of direct inheritance, it was assumed that each part of the body of a parent, each of its cells, conveys the characteristics of its structure to its offspring. The hypothesis of indirect inheritance argued that the sex products are formed apart, therefore the lifetime changes of parents are not transmitted to their descendants.

Charles Darwin adhered to the first hypothesis, which was a mistake. That is why he could not refute one of the critics of his evolutionary theory, who wrote the following. If an animal has a new property, then it will give only ½ of this property to the next generation, and the next one will take only ¼, etc. In the end, the characteristic will disappear. Darwin could not argue, because he did not know that the characteristics of an organism are discrete, they do not mix and dissolve.

Mendel conducted a statistical analysis of inheritance of characteristics in a number of generations. As an object of research, he chose pea plants. It was a very good choice. Such characteristics as the color of seeds and flowers, the wrinkling of seeds are in different chromosomes (i. e. they are inherited independently of each other) and they do not have an intermediate manifestation of the feature (for example, the seed can be either yellow or green but not mixed color). Of course, Mendel knew nothing of the linked inheritance, that the genes and alleles affect each other. If this were observed in the examined pea characteristics, Mendel's experiment might not succeed.

Gregor Mendel and the laws of heredity that he discovered - the 1860s

Mendel proved the discreteness of hereditary traits. They do not mix and dilute, just one trait suppresses another. Mendel developed a hybridological method of research. But most importantly, for the first time in the history of genetics Mendel formulated three laws: the uniformity of hybrids of the first generation (dominance of characteristic), splitting in the second generation, independent inheritance of traits.

However, in those days the history of genetics had not yet begun. Mendel was a monk, not a scientist, so his research was not given much importance. Only at the beginning of the 20th century, when many scientists experimentally confirmed the laws of Mendel on different plants and animals, his works were deservedly evaluated.

The beginning of the 20th century was a stormy stage in the development of genetics. At this time, the term "genetics" appears. The definitions of "gene", "genotype" and "phenotype" were given. The phenomenon of linked genes was discovered, W. Bateson opened the law of purity of gametes, etc. In 1910, together with other scientists, T. Morgan developed the chromosome theory that generalizes and explains all previously made discoveries in the history of genetics.

Thomas Morgan was researching chromosomes, discovered crossing over - the 1910s and later

In subsequent years, genetics and evolutionary theory were linked together. Evolution finds explanation from the point of view of the genetic laws.

Scientists knew that hereditary information is transmitted through chromosomes, but they did not know whether the protein or DNA is responsible for that. In the 40's it became clear that DNA is the carrier of heredity. Some researchers had been transferring DNA from one bacteria to another, in which the traits of the first group appeared.

When new methods of chemistry and physics appeared it became possible to investigate the structure of DNA. This was done by Crick and Watson in 1953. It turned out that the DNA molecule consists of two polynucleotide chains, twisted into a helix. Each of the DNA strands is a template for the synthesis of a new chain. Such doubling of DNA underlies heredity.

Francis Crick and James Watson explained the structure of DNA - the 1950s

Scientists realized that the sequence of nucleotides determines the structure of the protein molecule. Each amino acid of proteins is encoded by three consecutive nucleotides of the DNA.

In the 1970s, genetic engineering appeared. Scientists began to change the genomes of some organisms. Molecular basis of physiological processes was started to research.

In the last decade of the 20th century, the genomes of several simple organisms were sequenced. At the beginning of the 21st century (2003), a project of decoding (determining the sequence of nucleotides in chromosomes) of the human genome was completed.

Logo of Human Genome Project

Currently, there are databases of the genomes of many organisms. The existence of such the base for the human genome is great importance in the prevention and investigation of many diseases.