Chapter 13 PATTERNS OF INHERITANCE

Chapter 13 PATTERNS OF INHERITANCE - Chapter 13 MENDEL AND...

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Chapter 13 MENDEL AND THE GENE Why do we look like family members or not? History *It started with farmers and botanists *Knight used pure breeding peas, one variety with purple flowers, one variety with white flowers. *Crossing the two varieties he found that the offspring all had purple flowers. *When he crossed the offspring, some had purple flowers, some had white flowers. *Conclusion: some traits have a stronger tendency to appear than others. No Numbers *Mendel, an Austrian monk, repeated Knight’s experiments: *Also used true-breeding peas and studied 7 different traits, fig 13.2. *Cross-fertilized peas showing two variations of the same trait, ex. round peas vs. wrinkled peas. Mendel Studied a Single Trait *Mendel cross-fertilized two plants, one with white flowers with one with purple flowers. The hybrids, the F1 generation , all had purple flowers. *Studying one trait through cross-fertilization is termed a monohybrid cross . *Mendel allowed F1 generation plants to self- fertilize. *Their offspring, the F2 generation , expressed (demonstrated) both purple and white flowers. The ratio of plants with purple to white flowers was always 3:1. *Where did these white flowered plants come from? *The F1 generation plants all resembled only parent plant; i.e. one variation of the trait is dominant . *The F2 generation showed plants with both variations of the character, purple and white. The variation of the trait that was only seen in the F2 generation (white flowers) is recessive . *The F2 generations were allowed to self-fertilize.
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Chapter 13 PATTERNS OF INHERITANCE - Chapter 13 MENDEL AND...

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