12 1 Origins of Hereditary Science I Mendels

12. 1 Origins of Hereditary Science I. Mendel’s Breeding Experiments A. Gregor Mendel 1. Monk that lived in Austria in the 1800’s 2. “Father of modern genetics” 3. Conducted experiments by crossing pea plants a. Cross means “to mate or breed two individuals” II. Features of Pea Plants A. Benefits of using pea plants 1. Contrasting Traits a. Characters = physical features that are inherited b. Traits = one of several possible forms of a character 1. ex - white or purple flower color c. Hybrids 1. the offspring of a cross between parents that have different traits 1

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2. Self-Pollination a. garden pea plants have both male & female reproductive parts b. able to self fertilize c. also able to cross-pollinate 3

3. Easy to Grow a. The garden pea is a small plant that needs little care, matures quickly, & produces many offspring III. Mendel’s First Experiments A. Monohybrid cross 1. A cross that studies one set of traits a. ex – purple vs. white flowers B. Mendel’s experiments used three steps 1. Allowed plants to self pollinate for several generations a. plants were pure bred or true breeding b. Used true breeding plants at parental generation (P generation) 2. Crossed two P generations with contrasting traits. a. ex – purple & white flowers b. offspring called first filial generation or F 1 generation 3. Allowed the F 1 generation to cross pollinate. a. Called this generation the second filial generation (F 2 generation) 4

IV. Ratios in Mendel’s Results A. All of the plants expressed the same trait in the F 1 generation 1. ex – white flowers crossed with purple flowers produced all purple B. In the F 2 generation the missing trait reappeared 1. It was a 3 -to-1 ratio purple to white. 2. For each of the seven traits Mendel noticed a similar 3 to-1 ratio 5

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