Gregor Mendel pod shape, unripe pod color, flower location, and plant height. He first focused on seed shape, which was either angular or round. Between 1856 and 1863 Mendel cultivated and tested some 28,000 plants, the majority of which were pea plants ("Pisum sativum"). This study showed that, when true-breeding different varieties were crossed to each other (e.g., tall plants fertilized by short plants), in the second generation, one in four pea plants had purebred recessive traits, two out of four were hybrids, and one out of four were purebred dominant. His experiments led him to make two generalizations, the Law of
Introduction to genetics Introduction to genetics Genetics is the study of heredity and variations. Heredity and variations are controlled by genes—what they are, what they do, and how they work. Genes inside the nucleus of a cell are strung together in such a way that the sequence carries information: that information determines how living organisms inherit various features (phenotypic traits). For example, offspring produced by sexual reproduction usually look similar to each of their parents because they have inherited some of each of their parents' genes. Genetics identifies which features are inherited, and explains how these features pass from generation to generation. In