2. Genetics Mendel

3. Heredity  Heredity is the passing of traits from parents to offspring. Heredity

4. Genetics  Genetics—the study of how traits are passed from parents to offspring. Genetics  Gregor Mendel – “The father of genetics”

5. Gregor Mendel  Austrian monk studied genetics in the 1850’s.  Did controlled breeding experiments with pea plants because: Reproduced quickly – lots of data Reproduced quickly – lots of data Easily observed traits (flower color, pea shape) Easily observed traits (flower color, pea shape) Could control which pairs of plants reproduced Could control which pairs of plants reproduced

6. Pollination in pea plants  Sexual reproduction  Pollen (sperm) from stamen lands on pistil (eggs)  2 ways of pollination: Self-pollination Self-pollination Cross-pollination Cross-pollination

7. Self-pollination

8. Cross-pollination

9. Mendel’s experiments  Started with “True-Breeding Plants” (plants that produce offspring with traits that match the parent when self-pollinated)  Cross-pollinated hundreds of plants for different traits

10. Mendel’s results First-Generation Crosses

11. Hybrid   Science Use the offspring of two animals or plants with different forms of the same trait   Common Use having two types of components that perform the same function, such as a vehicle powered by both a gas engine and an electric motor

12. Mendel’s results Second-Generation (Hybrid) Crosses

14. Mendel’s results  All first generation hybrid plants always only exhibit one of the traits.  Second generation hybrid plants express the dissapeared trait (25% of the offspring)

15. Mendel’s conclusions  Two factors, one from each sperm and one from each egg, control each inherited trait.

16. Mendel’s conclusions  First generation hybrids had one factor for each trait: Purple x White = (one purple factor, one white factor) Purple x White = (one purple factor, one white factor) Why only purple flowers? Why only purple flowers?  Mendel hypothesized: Purple factor is dominant – blocks white factor

17. Mendel’s conclusions  Dominant trait: genetic factor that blocks another genetic factor  Recessive trait: genetic factor that is blocked by the presence of a dominant factor

18. Mendel’s conclusions  First generation hybrid x first generation hybrid (Each plant has one dominant factor and one recessive factor)  75% of plants purple (at least one dominant factor)  25% of plants white (two recessive factors)