If you have completed a first-year high school biology course, some of this chapter will serve as a review for the basic concepts of Mendelian genetics. For other students, this may be your first exposure to genetics. In either case, this is a chapter that should be carefully mastered. Spending some time with this chapter, especially working genetics problems, will give you a solid foundation for the extensive genetics unit in the chapters to come. | Chapter 14 Mendel and the Gene Idea Overview: Drawing from the Deck of Genes What genetic principles account for the transmission of traits from parents to offspring? 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 Concept : 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 Mendel’s Experimental, Quantitative Approach Mendel chose to work with peas Because they are available in many varieties Because he could strictly control which plants mated with which Crossing pea plants Figure 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 (F1) 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 . | Chapter 14 Mendel and the Gene Idea Overview: Drawing from the Deck of Genes What genetic principles account for the transmission of traits from parents to offspring? 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 Concept : 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 Mendel’s Experimental, Quantitative Approach Mendel chose to work with peas Because they are available in many varieties Because he could strictly control which plants .
