Basics of genetics and Mendel’s laws

Genetics is the science of heredity and variation; the term was introduced by W. Bateson in 1906. Heredity is the passing of features and properties to descendants, while variation is the ability of organisms to form new features and to differ from each other; they are opposite but linked properties. A gene is a unit of hereditary information; the sum of all genes of an organism is the genotype and the sum of all its features and properties is the phenotype; the phenotype depends on the genotype and, to some degree, on the environment. Genetic symbols: cross “×”, mother “♀”, father “♂”, parental generation P, gametes G, first-generation hybrids F1, second F2; the offspring of crossing F1 with a recessive homozygote (back-cross) is Fb. Stages of genetics: 1) the laws of G. Mendel, 2) T. Morgan’s chromosome theory, 3) application of physics, chemistry and cybernetics (electron microscope, X-ray structure analysis); today also the era of reading genomes and genetic engineering.