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Unformatted text preview: Sheet1 Page 1 Mendel and the Gene Idea I. The laws of heredity must explain both stability of species and variation within the species. A. Parents pass on their general traits to their offspring. B. Offspring are not exactly like either parent but vary in their characteristics. II. Gregor Mendel took the first steps toward explaining this with his discovery of the laws of heredity in the early 1860s. A. Mendel was an Austrian monk who taught natural science and worked on plant breeding experiments. B. Most plant and animal breeders of the time believed in the blending theory of inheritance. 1. It held that both sexes contributed equally to the characteristics of the offspring. 2. Offspring were thought to be intermediate in form between the 2 parents, such as pink flowers from a cross between whi 3. When red or white flowers appeared in offspring, they were attributed to instability of the genetic material. 4. This theory presented a problem to Charles Darwin, who could show no genetic basis for his theories on evolution. 1. His mathematical background led him to use statistical methods in his studies. 2. He performed preliminary studies on plants and animals before choosing to work with the garden pea. 3. The plants were easy to cultivate, with a short generation time. a) While usually self-pollinating, they could be cross-fertilized easily. b) Many varieties were available in true-breeding strains. c) Mendel chose 22 varieties for his experiments, using simple traits. 4. Mendel chose to study traits such as seed shape, seed color, and flower color. 5. He kept careful records of offspring and their inheritance of individual traits, as observed objectively. 6. He used the mathematical laws of probability to interpret the results. 7. Mendel developed a particulate theory of inheritance. A. These experiments involved monohybrid crosses. 1. If the blending theory were true, the offspring should have characteristics intermediate between those of the parents....
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- Spring '09