Basics of Medical Genetics - Buzhiyevska T.I. 2001

General Genetics
History of the Development of Genetics and Medical Genetics as a Science

The history of the Selection/4.html">Development of Genetics as a science officially begins in 1900 and is divided into 6 periods:

1. The triumphant rise of Mendelism.

2. The ESTABLISHMENT OF THE Chromosomal Basis of heredity.

3. The discovery of induced mutagenesis.

4. The Development of biochemical genetics.

5. The mastery of the foundations of Molecular Genetics.

6. The Emergence of mobile (modern) genetics.

Until the 1970s and 1980s, the majority of geneticists

believed that the fundamental patterns of heredity and Variability in organisms had already been studied, meaning that genetics as a fundamental science had achieved its primary goal. Therefore, in the future, the attention of scientists and their research should be directed toward the genetics of various organisms, including human and medical genetics, and their applied aspects—biotechnology, the decoding of genetic programs, the creation of new hybrid genomes and genotypes, and new living beings in the interests of "all mankind," individual populations, social classes (or even groups), or, more rarely, each specific human being.

In this regard, humanitarian concerns fall entirely on the shoulders of medically educated physicians who must stand guard over the health and life of every individual (rather than just the state or society as a whole), as physicians in all countries have done since the time of Hippocrates.

The BOUNDARIES OF THE historical periods in the development of genetics as a science are not rigidly defined; they are entirely conventional, as each subsequent period originated within the depths of the previous one and continued throughout all the following ones. The names of the periods reflect the main direction of scientific research during that particular time.

The main feature of the development of genetics is the existence of a vast prehistoric period (spanning the entire history of humankind) during which the accumulation and analysis of factors of heredity and variability in Multicellular Organisms, including humans, took place. A review of cultural and religious artifacts indicates that the knowledge acquired by humanity was at times lost, forgotten, or sometimes simply neglected; scientific research was frequently banned due to ignorance or political motives. Descriptions of pedigrees, beginning with Adam and Eve, which included consanguineous relations, Inbreeding, or incestuous marriages involving the inheritance of specific types of pathologies, are provided in the Bible. The prevalence in certain populations of individuals carrying rare genes, or those with special traits distinct from the rest (such as left-handedness and right-handedness), is also reflected in ancient historical texts.

The first documented medical-genetic consultation is recorded in the Talmud: it was forbidden to perform ritual circumcision on infant boys whose older brothers and maternal uncles suffered from bleeding disorders. Here, we have not only the recognition of the heredity of hemophilia, but also a remarkably accurate emphasis on the X-linked recessive inheritance of this condition.

The fundamental classical laws of heredity were discovered by G. J. Mendel (Fig. 1) in 1865, although they had existed and functioned always, ever since the appearance of life on our planet. However, these laws subsequently "vanished into oblivion" for various reasons until 1900, when three scientists from different countries independently rediscovered them: de Vries (Netherlands), Tschermak (Austria), and Correns (Germany). Nevertheless, the laws of heredity permanently retained the name of Mendel's Laws, defining a distinct branch of biology known as Mendelism. The History of Human genetics is actually considered a science existing since 1865 (rather than 1900), based not on Mendel's work concerning the inheritance of qualitative, alternative traits, but on the works of Galton, which deal with the inheritance of Quantitative Traits. This very year is considered the beginning of the emergence of eugenic concepts and research into the Methods and conditions for influencing human hereditary qualities.

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Fig. 1. Gregor Johann Mendel (1822–1884)

Czech scientist, founder of the science of heredity, who first discovered its laws, known as Mendel's laws

The results of these studies later formed The basis of eugenics—both positive and negative—which eventually degenerated into the pseudoscience of racial hygiene: racism and fascism. For decades, humanity lacked a scientific refutation of the futility and falsity of eugenic ideas and endeavors.

Nowadays, there is no doubt that eugenics has neither philosophical nor moral grounds, neither biological justification nor genetic foundation. Firstly, in the breeding of plants, insects, and animals, humans act in their own interests, disregarding the interests of living beings they consider inferior to themselves. Who, then, is to decide The Fate of a human being? One cannot determine the fate of a system while being a part of that very system. Secondly, we do not know the future evolutionary program of humanity, nor which Gene variants will confer a selective advantage in the environment we ourselves are altering; therefore, we have no right to destroy genes that may seem harmful today. Thirdly, mental retardation is predominantly the result of a recessive pathology that manifests clinically only in the homozygous state. Such patients will not transmit diseases to their descendants, but only one of two mutant genes. Their descendants will be as healthy as their grandparents and grandfathers. The sterilization of patients will not lead to a decrease in the number of idiots, the mentally ill, or criminals, just as it did in the 1930s in California, where 10,000 mentally retarded individuals were sterilized.

The number of patients and disease carriers is regulated by population laws themselves (biological and genetic). Social laws, legal regulations, and political decrees cannot influence this.

Everyone is familiar with Mendel's 3 laws:

1. The uniformity of first-generation hybrids resulting from the crossing of organisms that stably differ in alternative traits: the dominant gene is manifested in the heterozygous state.

2. The segregation of second-generation hybrids (crossing heterozygous organisms for a qualitative alternative trait) in a 3:1 ratio (three PARTS OF THE offspring showing the dominant trait and one part showing the recessive trait).

3. The independent assortment of traits in the offspring of parents differing in two or more alternative qualitative traits.

Inheritance determined by these laws is called Mendelian, and pathology transmitted to descendants according to Mendel's laws is termed Mendelian. Thus, the truth of scientific foundations prevailed. Whether sincerely or insincerely mistaken, politicians of the former USSR imbued science, as well as morality, with a class character, appending their ideological Conclusion to so-called bourgeois teachings, branding incomprehensible sciences, and pitting "Mendelism" along with "Weismannism-Morganism" against materialism and Marxism-Leninism. This very foundation served as the rationale for banning genetic research in our country, prohibiting the teaching of genetics at all levels of education, and leading to the moral and physical destruction of scientists and specialists in this field of knowledge, as well as the destruction of scientific and pedagogical literature. The organizer and executor of this anti-scientific and antihuman policy was T. D. Lysenko, and its consequence was the upbringing of nearly three generations of physicians who are ignorant of genetics and differ from medical professionals in other countries by their lack of genetic thinking, which negatively impacts their professionalism.