5.1 Lecture 9: Mendel and his Peas - 1

5.1.1 Keywords

英文	中文	解释
Trait	性状	characteristic
Heredity	遗传	the passing of traits from parents to offspring
Genetics	遗传学	the study of how traits are passed on
Self-pollination	自花授粉	a form of pollination when pollen from one plant lands on the pistil of a flower on the same plant
Cross-pollination	异花授粉	a form of pollination when pollen from one plant reaches the pistil of a flower on a different plant
Pistil	雌蕊	female organs of a flower
Stigma	柱头	the part of a pistil that receives the pollen during pollination
Stamen	雄蕊	male organs of a flower
Anther	花药	the part of a stamen that contains the pollen
Pollen	花粉	consists of pollen grains, which produce male gametes (sperm cells)
True-breeding	纯种	organisms whose offspring are the same as the parent
Hybrid	杂种	organisms from true-breeding parents with different traits

5.1.2 Lesson outline

A. Early Ideas about Heredity
1. Heredity is the passing of traits from parents to offspring.
2. In the 1850s, Gregor Mendel, an Austrian monk, performed experiments that helped answer questions about how traits are inherited.
3. Genetics is the study of how traits pass from parents to offspring.

B. Mendel’s Experimental Methods
1. Pea plants were ideal for genetic studies because they reproduce quickly; they have easily observed traits; and the experimenter can control which pairs of plants reproduce.
2. Mendel controlled which plants pollinated other plants.
    a. When a(n) true-breeding plant self-pollinates, it always produces offspring with traits that match the parent.
    b. By cross-pollinating plants himself, Mendel was able to select which plants pollinated other plants.
3. With each cross-pollination Mendel did, he recorded the traits that appeared in the offspring.

C. Mendel’s Results
1. Mendel’s crosses between true-breeding plants with purple flowers produced plants with only purple flowers. Crosses between true-breeding plants with white flowers produced plants with only white flowers.
2. Crosses between true-breeding plants with purple flowers and true-breeding plants with white flowers produced plants with only purple flowers.
3. The first–generation purple-flowering plants are called hybrid plants.
4. When Mendel cross-pollinated two hybrid plants, the trait that had disappeared in the first generation always reappeared in the second generation.
5. Mendel analyzed the data from many experiments on seven different traits. He always noted a 3:1 ratio; for example, purple flowers grew from hybrid crosses three times as often as white flowers.