Chapter 14 - Mendel and the Gene Idea

Chapter 14 - Mendel and the Gene Idea - Chapter 14 Class...

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Chapter 14 Class Notes – Mendel and the Gene Idea – Page 1 Max Sauberman AP Biology – Mr. Schilp Chapter 14 Mendel and the Gene Idea Overview of Genetics: Various genetic principles account for the passing of traits from parent to offspring. The blending hypothesis is the idea that genetic material from the two parents blend together, in a similar fashion to how blue and yellow blend to form green. The particulate hypothesis is the idea that parents pass on genes, specific heritable units. Gregor Mendel documented a particulate mechanism through his experiments with garden peas. Mendel’s Laws: Mendel used the scientific approach to identify two laws of inheritance. Mendel discovered the basic principles of heredity by breeding garden peas in carefully planned environments. Advantages of pea plants for genetic study: There are many varieties with distinct heritable features, or characters. Character variations are called traits. Mating of the pea plants can be completely controlled. Each pea plant has sperm-producing organs (stamens) and egg-producing organs (carpels). Cross-pollination, fertilization between different plants, can be achieved by dusting one plant with pollen from another. Mendel’s Experiment: Mendel chose to track only those characteristics that varied in an either-or method. He used varieties that were true-breeding; in plants that produced offspring of the same variety when they self- pollinated (and are thus homozygous). In a typical experiment, Mendel mated two contrasting true-breeding varieties, in a process called hybridization. The true-breeding parents are the P generation. The hybrid offspring of the P generation are called the F 1 generation (first filial generation), and are all heterozygous. When F 1 individuals self-pollinate, the F 2 generation is produced.
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Chapter 14 Class Notes – Mendel and the Gene Idea – Page 2 Discovering the Law of Segregation: When Mendel crossed contrasting true-breeding white and purple flowered pea plants, all of the F 1 hybrids were purple. When Mendel crossed the F 1 hybrids, many of the F 2 plants had purple flowers, but some had white flowers. Mendel discovered a ratio of about 3:1 purple to white flowers in the F 2 generation. Mendel’s reasoning: Mendel reasoned that only the purple flower factor was affecting flower color in the F 1 hybrids. Mendel called the purple flower color a dominant trait and the white flower color a recessive trait. Mendel observed the same pattern of inheritance in six other pea plant characters, each represented by two traits. What Mendel called a heritable factor is now a gene. The white flowers in the F 2 generation (that were not present in F 1 prove that chromosomes are separated. The Seven Pea Plant Characters:
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This note was uploaded on 03/17/2011 for the course BIO 101 taught by Professor Sullivan during the Spring '08 term at Harvard.

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Chapter 14 - Mendel and the Gene Idea - Chapter 14 Class...

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