2. Gregor Mendel and Genetics

3. The Work of Mendel Genetics = scientific study of heredity Heredity = characteristics that are passed on to the next generation Gregor Mendel (1800’s) –Grew up as a peasant farmer –Austrian Monk, high school science teacher, in charge of monastery gardens. –Used garden peas for experiments

4. Mendel was successful because:  peas are self-pollinating (inherit all characteristics from plant that bore them)  Had true breeding stock = basis for experiment  Can cross pollinate (uses 2 parents)  Controlled experiment  Kept careful records !

6. Traits studied Chose several traits that were true-breeding and had two distinct forms  Seed shape: round vs wrinkled  Seed color: Yellow vs green  Gray seed coat vs white seed coat  Smooth pod shape vs constricted pod  Pod color = green vs yellow  Flower position = axial vs terminal  Height = tall vs short

7. Mendel’s Experiment P = parental generation, original pair, true breeding, tall x short Cross pollination: F1 generation = first filial generation results in hybrids (from parents with contrasting traits) results: all tall Self pollination: F2 generation = second filial generation ¾ tall, ¼ short

10. MENDEL’S CONCLUSION: “Factors” governed the expression of each trait (factors now called ?) Each trait = controlled by a pair of genes, two factors (ex. 1 for tall, 1 for short) Allele = different forms of a trait, one of the gene pair

11. Principle of Dominance 1 of the genes in a pair may prevent the other gene from being expressed. Dominant gene = one which masks the other in a pair Recessive gene = one which is hidden (may reappear in F2) Dominant allele = expressed by a capital letter (ex. Y = yellow) Recessive allele = lower case (ex. y = green)

12. Principle of Segregation Members of each pair of genes separate during gamete formation **********