Pediatric Medical Genetics - S.I. Smiian 2003

General Principles of Medical Genetics
Historical Background

Genetics, derived from the Greek word genetikos (meaning "pertaining to birth"), explores the principles of heredity and variation. As a science, genetics was born out of practical human needs. Since ancient times, animal breeding has relied on Hybridization, or the crossing of different breeds. The fundamental patterns of how traits and characteristics are inherited across generations were discovered by Gregor Mendel, a high school physics and natural history teacher and Augustinian monk from the town of Brünn (now Brno, Czech Republic). He presented his research in 1865 at a meeting of the Natural Science Society in Brno. Although Mendel's theory eventually became a cornerstone of classical biology, his work initially failed to capture the attention of his contemporaries. The success of Mendel's work can be attributed to two essential qualities of a true scientist: The ability to ask nature the right question and the ability to correctly interpret nature's answer. Furthermore, Mendel was exceptionally industrious and meticulous—qualities that, alongside intellectual brilliance, define a true scientist. Mendel conducted this research for over eight years, cultivating and thoroughly studying nearly 10,000 pea plants before daring to publish his modest findings.

Mendel realized that the only way to get a clear answer from nature was to ask it a very simple question. Therefore, for his hybridization experiments, he chose pea varieties that differed from one another in only a single, well-defined trait (such as color, height, or flower shape). In every generation, records were kept for each individual trait. The quantitative and qualitative analysis of traits in subsequent generations, along with the individual progeny analysis of each plant, introduced revolutionary new Methods FOR STUDYING heredity, collectively known as genetic analysis. Based on his research, Mendel formulated three laws of inheritance: First—the law of dominance, or uniformity of characters in the $F_1$ hybrids (crossing green and yellow peas yielded exclusively yellow hybrids, a phenomenon Mendel termed dominant); Second—the law of segregation in the $F_2$ generation (crossing the $F_1$ hybrids produced both yellow and green plants, with the green trait designated as recessive); Third—the law of independent assortment.

Mendel's theory was so far ahead of the scientific knowledge of his time that it is hardly surprising his contemporaries overlooked this groundbreaking discovery.

It was not until 1900, independently and nearly simultaneously in three different countries (de Vries in the Netherlands, Correns in Germany, and Tschermak in Austria), that researchers working with different biological models rediscovered these crucial Patterns of inheritance. The year 1900 is widely regarded as the rebirth of genetics. Early in the 20th century, at the suggestion of Danish botanist Wilhelm Johannsen, these fundamental units of heredity were named genes.

In the Soviet Union, prominent schools of genetics emerged during the 1920s. Scientists such as N.K. Koltsov, A.S. Serebrovsky, M.M. Zavadovsky, S.S. Chetverikov, G.I. Roskin, and N.P. Dubinin made monumental contributions to Gene theory. Brilliant, world-Class research in plant genetics was also conducted by Academician N.I. Vavilov, whose profound impact on science remains undervalued to this day. By the early 1930s, Soviet genetics held a leading position globally. However, the subsequent Stalinist regime suppressed the discipline, Setting Soviet genetics back by many decades. Reinstated 25 to 30 years ago, genetics is now experiencing explosive growth, serving as a guiding light in the Diagnosis, Treatment, and Prevention of Hereditary Disorders in patients' families.