If the flowers are covered to en sure that insects

Info icon This preview shows pages 4–7. Sign up to view the full content.

View Full Document Right Arrow Icon
on the top of the egg-carrying carpel of the same plant. If the flowers are covered to en- sure that insects cannot carry pollen from one flower to another,the sperm and eggs from the same plant combine within the bud to give rise to peas—the seeds of the next gen- eration of pea plants. Mendel manipulated this process by opening the flower buds and cutting off the pollen-bearing structures, called anthers, from some flowers. Using anthers taken from different flowers, Mendel could control exactly which sperm was used to fertilize which eggs (Figure 3-2). He started with two varieties of plants, one whose ancestors produced only round, smooth peas and another from a long line of plants that produced only wrin- kled peas. He cross-fertilized the two varieties. In other words, he used the pollen of one variety to fertilize the egg of the other variety, creating hybrid offspring. This was done by brushing the female parts of flowers of the round-seeded line with the male pollen from the wrinkled-seeded variety, and vice versa. If blending were indeed the basis of heredity, as discussed earlier, all of the hybrid seeds from these experimental crosses would have been partially wrinkled in texture, intermediate between the two parental forms.That did not happen. Remarkably, the hybrid peas of this first generation, called the or first filial , generation, were all round. F 1 , Pea Hybridization: Life Cycle: Observe pollination of a pea plant. Pea Hybridization: Fertilization: Watch pollen tube formation. Pea Hybridization: The F 1 Generation: The seed grows into a mature plant.
Image of page 4

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
3-1 How Are Traits Passed from Generation to Generation? 65 Plant Height Flower Color Flower Position Pod Color Pod Shape Seed Color Seed Shape Round Wrinkled White Purple At tips of branches (terminal) At leaf junctions (axial) Tall (6 _ 7 feet) Dwarf (9 _ 18 inches) Yellow Green Constricted Inflated Yellow Green Figure 3-1 The seven traits that Mendel studied. Note that each trait appears in one of two distinct forms. When these hybrid round peas grew into mature plants and were permitted to self- fertilize, some of the many “grandchildren” of the original pure-breeding varieties—the or second filial , generation—were round and some were wrinkled. In fact, 5,474 of the generation were round, and 1,850 were wrinkled, a ratio of about three round F 2 F 2 ,
Image of page 5
66 C HAPTER 3 Mendelian Genetics: How Are Traits Inherited? 1 2 Petals Pollen Amputated anthers Anthers ( ) Ovary with ovules Stigma Carpel ( ) Mendel took pollen from the anthers of a plant exhibiting one form of a trait. He brushed the pollen onto the stigma of a plant showing a different form of the trait. The anthers of the second plant were first removed to prevent self- fertilization. Flower of a pea plant (a) Cross-fertilization (b) Figure 3-2 (a) Flower of a pea plant, cut to show male and female flower parts. (b) Using artificial cross-fertilization, Mendel controlled matings between plants.
Image of page 6

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern