1. DO NOW : Can you roll your tongue? Do you have a widow’s peak? Are your earlobes attached or do they dangle? Objectives: 1.Explain the relationship between traits and heredity. 2.Describe the experiments of Gregor Mendel. 3.Differentiate between dominant and recessive traits. 4/14

2.   Gregor Mendel was born in 1822 in Heinzendorf, Austria.  At age 21, Mendel entered a monastery.  Performed many scientific experiments in the monastery garden.  Mendel discovered the principles of heredity, the passing of traits from parents to offspring. Who was Gregor Mendel?

3.   Mendel used garden pea plants for his experiments.  Self-Pollinating Peas have both male and female reproductive structures. So, pollen from one flower can fertilize the ovule of the same flower.  Pea plants also grow quickly, allowing him to produce many generations within a short time span.  When a true-breeding plant self pollinates, all of the offspring will have the same trait as the parent. Unraveling the Mystery

4.   Pea plants can also cross- pollinate.  Pollen from one plant fertilizes the ovule of a flower on a different plant.  The image shows cross- pollination and self- pollination. Unraveling the Mystery

5.   Characteristics  Mendel studied only one pea characteristic at a time.  A characteristic is a feature that has different forms in a population. (Ex. Eye color)  Different forms of a characteristic are called traits. (Ex. Brown and Blue) Unraveling the Mystery, continued

6.   Mix and Match  Mendel was careful to use plants that were true breeding for each of the traits he was studying.  This allowed him to know what to expect if his plants were to self- pollinate. Unraveling the Mystery, continued

7.   Mendel crossed pea plants to study seven different characteristics.  He noticed that one trait was always present in the first generation, and the other trait seemed to disappear.  Mendel called the trait that appeared the dominant trait.  The trait that seemed to fade into the background was called the recessive trait. Mendel’s First Experiments

8.   To find out more about recessive traits, Mendel allowed the first-generation plants to self-pollinate.  In each case some of the second-generation plants had the recessive trait. Mendel’s Second Experiments

9.   Ratios in Mendel’s Experiments  The recessive trait did not show up as often as the dominant trait.  Mendel decided to figure out the ratio of dominant traits to recessive traits. Mendel’s Second Experiments, continued

10.   In all cases the ratio was about 3:1 dominant : recessive. Mendel’s Second Experiments, continued

11.   Gregor Mendel – Gone But Not Forgotten  Mendel realized that his results could be explained only if each plant had two sets of instructions for each characteristic.  Mendel’s work opened the door to modern genetics. Mendel’s Second Experiments, continued

12. DO NOW : Why did Mendel decide to use pea plants to further his understanding of heredity? Objectives: 1.Explain the relationship between traits and heredity. 2.Describe the experiments of Gregor Mendel. 3.Differentiate between dominant and recessive traits. 4/15