Mendel’s Laws
Mendel’s Laws, principles of hereditary transmission of physical characteristics. They were formulated in 1865 by the Augustinian monk Gregor Johann Mendel . Experimenting with seven contrasting characteristics of pure-breeding garden peas, Mendel discovered that by crossing tall and dwarf parents, for example, he got hybrid offspring that resembled the tall parent rather than being a medium-height blend. To explain this he conceived of hereditary units, now called genes, which often expressed dominant or recessive characteristics. Formulating his first principle (the law of segregation), Mendel stated that genes normally occur in pairs in the ordinary body cells, but segregate in the formation of sex cells (eggs or sperm), each member of the pair becoming part of the separate sex cell. When egg and sperm unite, forming a gene pair, the dominant gene (tallness) masks the recessive gene (shortness). To corroborate the existence of such hereditary units, Mendel went on to interbreed the