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DO NOW :. 4/14. Can you roll your tongue? Do you have a widow’s peak? Are your earlobes attached or do they dangle?. Objectives: Explain the relationship between traits and heredity. Describe the experiments of Gregor Mendel. Differentiate between dominant and recessive traits.
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DO NOW: 4/14 Can you roll your tongue? Do you have a widow’s peak? Are your earlobes attached or do they dangle? • Objectives: • Explain the relationship between traits and heredity. • Describe the experiments of Gregor Mendel. • Differentiate between dominant and recessive traits.
Who was Gregor Mendel? • 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.
Unraveling the Mystery • 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 • 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, continued • 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 • 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.
Mendel’s First Experiments • 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 Second Experiments • 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, continued • 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 • In all cases the ratio was about 3:1 dominant : recessive.
Mendel’s Second Experiments, continued • 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.
DO NOW: 4/15 Why did Mendel decide to use pea plants to further his understanding of heredity? • Objectives: • Explain the relationship between traits and heredity. • Describe the experiments of Gregor Mendel. • Differentiate between dominant and recessive traits.
