Mendelian genetics T square

Mendelian genetics T square - Chapter 14 Mendel and the...

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Unformatted text preview: Chapter 14 Mendel and the Gene Idea One possible explanation of heredity is a blending hypothesis The idea that genetic material contributed by two parents mixes in a manner analogous to the way blue and yellow paints blend to make green An alternative to the blending model is the particulate hypothesis of inheritance: the gene idea Parents pass on discrete heritable units, genes Gregor Mendel Documented a particulate mechanism of inheritance through his experiments with garden peas Figure 14.1 Concept 14.1: 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 experiments Crossing pea plants Figure 14.2 1 5 4 3 2 Removed stamens from purple flower Transferred sperm- bearing pollen from stamens of white flower to egg- bearing carpel of purple flower Parental generation (P) Pollinated carpel matured into pod Carpel (female) Stamens (male) Planted seeds from pod Examined offspring: all purple flowers First generation offspring (F 1 ) APPLICATION By crossing (mating) two true-breeding varieties of an organism, scientists can study patterns of inheritance. In this example, Mendel crossed pea plants that varied in flower color. TECHNIQUE TECHNIQUE When pollen from a white flower fertilizes eggs of a purple flower, the first-generation hybrids all have purple flowers. The result is the same for the reciprocal cross, the transfer of pollen from purple flowers to white flowers. TECHNIQUE RESULTS Some genetic vocabulary Character: a heritable feature, such as flower color Trait: a variant of a character, such as purple or white flowers Mendel chose to track Only those characters that varied in an either- or manner Mendel also made sure that He started his experiments with varieties that were true-breeding In a typical breeding experiment Mendel mated two contrasting, true-breeding varieties, a process called hybridization The true-breeding parents Are called the P generation The hybrid offspring of the P generation Are called the F 1 generation When F 1 individuals self-pollinate The F 2 generation is produced Mendel discovered A ratio of about three to one, purple to white flowers, in the F 2 generation Figure 14.3 P Generation (true-breeding parents) Purple flowers White flowers F 1 Generation (hybrids) All plants had purple flowers F 2 Generation EXPERIMENT True-breeding purple-flowered pea plants and white-flowered pea plants were crossed (symbolized by...
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This note was uploaded on 04/07/2008 for the course BIO 1510 taught by Professor Unknown during the Fall '07 term at Georgia Institute of Technology.

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Mendelian genetics T square - Chapter 14 Mendel and the...

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