Biology 8.1 Origins of Genetics

1. Biology 8.1 Origins of Genetics Gregor Mendel and his experiments with peas

2. Heredity and Characteristics • Many of your characteristics; including the color and shape of your eyes and the color and texture of your hair, resemble those of your parents. • The passing of characteristics from parents to offspring is called heredity.

3. Mendel’s Experiments • The study of heredity begin more than a century ago with the work of Gregor Mendel. • Mendel carried out experiments in which he bred different varieties of garden peas. • Mendel was the first to develop rules that accurately predicted patterns of heredity.

4. Mendel’s Experiments • The patterns that Mendel discovered form the basis of genetics, the branch of biology that focuses on heredity. • Mendel cross bred garden peas with white flowers with garden peas with purple flowers. • Mendel focused on seven major character traits related to peas.

5. Mendel’s Experiments • Mendel’s initial experiments were monohybrid crosses. A monohybrid cross is a cross that involves one pair of contrasting traits. • For example, crossing a plant with purple flowers with a plant with white flowers is a monohybrid cross.

6. Mendel’s Experiments • Mendel carried out his experiments in three steps: • Step 1: Mendel allowed each variety of garden pea to self-pollinate for several generations. The ensured that each variety was true-breeding for a particular character trait. • For example, a true-breeding purple-flowering plant should produce only plants with purple flowers in following generations.

7. Mendel’s Experiments • Step 1: Thus these true breeding plants served as the parental generation in Mendel’s experiments. • This parental generation, or P generation, are the first two individuals that are crossed in a breeding experiment.

8. Mendel’s Experiments • Step 2: Mendel than cross-pollinated two P generation plants that had contrasting traits, such as purple flowers and white flowers. • Mendel called the offspring of the P generation the first filial generation or F1 generation. • He than examined each F1 plant and recorded the number of F1 plants showing each trait.

9. Mendel’s Experiments • Step 3: Finally, Mendel allowed the F1 generation to self-pollinate. He called the offspring of the F1 generation plants the second filial generation or F2 generation. • Again, each F2 plant was characterized and counted.

10. Mendel’s Experiments Mendel’s Results: • Each of Mendel’s F1 plants showed only one form of the trait, one color. • The contrasting form of the trait had disappeared, the second color. • When the F1 plant was allowed to self-pollinate, the missing color reappeared in some of the plants in the F2 generation. This mixture could be seen as a 3 to 1 ratio. • For each of the seven traits that Mendel studied, he found the same 3:1 ratio of contrasting traits in the F2 generation.

11. Key Concepts: • Gregor Mendel bred varieties of the garden pea in an attempt to understand heredity. Mendel observed that contrasting traits appear in offspring according to simple ratios. • In Mendel’s experiments, only one of the two contrasting forms or a character was expressed in the F1 generation. The other form reappeared in the F2 generation in a 3:1 ratio.

12. Computer Lab: • Use the internet to research and write a 1 page mini-report on Gregor Mendel and his experiments with peas. Describe his first experiments. • Put the information in your own words: DO NOT COPY, CUT, OR PASTE.