Читать книгу Horse Genetics - Ernest Bailey - Страница 42

Until the discovery of DNA structure, the word “gene” was an abstract term. People used the word to imply a mechanism or fundamental unit for hereditary traits, such as hair color, performance, or size. In this way genes were useful concepts, not unlike numbers or musical notation. We cannot see concepts, but we become aware of them through experience or education. Mendel never saw a gene, yet he was able to describe the basic principles of genetics from working with peas. Beginning with domestication approximately 5500 years ago, the first horse breeders recognized that offspring most resembled their parents. If one wanted a gray horse, then one of the parents needed to be gray. This was clear. However, the inheritance patterns for other traits, such as conformation, size, and performance, were more complex and this confounded breeders. Furthermore, horses are slow breeding, usually producing a single offspring and are thus not well suited for studying the principles of genetics. The genius of Mendel was to study plants, an organism with a short generation interval producing lots of seeds, select a small number of traits, understand them well, then extend that concept to all of heredity.

Genes ceased being abstract concepts in 1953 (Watson and Crick, 1953). The accurate description of DNA structure as the basis for heredity created a second avenue for understanding genetics. The structure, replication, modification, and function of DNA provided a concrete basis for what had been abstract concepts.