Genetics is the science that deals with heredity and the expression of genetic material, that is, the material that carries genetic information for all the functions of an organism. The term "heredity" refers to the process by which genetic information is transferred from parents to offspring. The term "expression" refers to the process by which the information carried by the genetic material of organisms manifests in characteristics that we can measure, perceive, or evaluate in a specific way. This book aims at a comprehensive overview of the basic principles of Genetics concerning animal organisms, with an emphasis on productive animals. 

The level of writing corresponds to a university-level teaching aid, thus requiring sufficient knowledge of high school Biology. The first chapter summarizes the basic principles of Classical Genetics and covers topics such as morphology, structure, composition, and functional processes of genetic material, chromosomal abnormalities, and genome mapping. 

The second chapter describes the inheritance of qualitative traits, the study of which is based on Mendel's rules. The third chapter deals with the basic concepts of Population Genetics, where the principles of Classical Genetics are applied to a group of individuals. The fourth chapter develops the concepts of Quantitative Genetics with an emphasis on traits of livestock interest. Finally, the fifth chapter presents the most important Applications of Genetics, mainly concerning animal production and Veterinary science. The language of the book is, of course, modern Greek, but the basic terms are also provided in English to familiarize readers with international terminology.