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Heredity

Heredity. Biology 1B Chapters 11 and 14. Section 11.1 Objectives. 1. Define heredity and identify the units of heredity. 2. Discuss the design, results and conclusions of Mendel’s monohybrid cross experiment. 3. Explain the principle of dominance and the principle of segregation. Heredity.

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Heredity

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  1. Heredity Biology 1B Chapters 11 and 14

  2. Section 11.1 Objectives 1. Define heredity and identify the units of heredity. 2. Discuss the design, results and conclusions of Mendel’s monohybrid cross experiment. 3. Explain the principle of dominance and the principle of segregation

  3. Heredity • From the same root word as “inherit” • Heredity describes the passing of traits from parents to offspring • Give examples of traits shared with family members:

  4. Problem • How are traits passed from parents to offspring?

  5. More Background • Many children resemble an aunt, uncle or grandparent more than they do their parents. • Some traits seem to “skip generations” • Often traits are expressed in children that are not observed in any other family member • ANY ACCEPTABLE HYPOTHESIS SHOULD BE ABLE TO ACCOUNT FOR THESE OBSERVATIONS

  6. Alternative Hypotheses: • Traits are inherited from only one parent • This seems true in many cases, because many children have a strong resemblance to either their mother or their father • Traits are inherited from both parents • This seems true in many cases also, because many children resemble both parents, and often have one trait similar to their father and another trait similar to their mother

  7. Gregor Mendel – Historical Perspective • Mendel was an Austrian monk in the mid 1800’s • Monks make contemplation and study a lifestyle. • Life at the monastery is largely self-sufficient. It is common for Monks to grow their own food.

  8. Gregor Mendel’s Experiments • Mendel grew peas for food at the monastery, and observed that the pea plants had a variety of distinct traits, such as flower color, that appeared to be inherited traits.

  9. Inherited Traits in Pea Plants

  10. “Monohybrid Cross” • Mono = one • Hybrid = cross breed • Mendel picked one trait at a time (“mono”) for his experiments, and cross bred (“hybrid”) pea plants for each trait to see what would happen • To track the effect of inheritance from one parent compared to the other, the parents must be different with regard to the trait being studied (“hybrid”) • The first generation in the experiment is labeled “P1” • P for Parents, 1 for 1st generation

  11. Monohybrid Cross – P1 Generation • This is a “hybrid” cross, because the parents are different for the trait being studied. • What trait is being examined in this experiment?

  12. Resulting offspring (F1) • F1, F for filial (greek for brothers) and 1 for 1st generation • In a cross between one purple flower parent and one white flower parent, all the offspring had purple flowers. • What hypothesis does this support?

  13. Section 11.2 Objectives 4. Use punnett squares to predict the probability of genetic crosses 5. Discuss the design, results and conclusions of Mendel’s dihybrid cross experiment. 6. Explain the principle Independent Assortment

  14. Section 11.3 Objectives: 7. Explain the following forms of inheritance: • Incomplete dominance • Codominance • Multiple alleles • Polygenic inheritance 8. Use pedigrees to analyze inheritance of alleles within families 9. Explain ABO blood type and Rh factor, and explain the inheritance of both traits

  15. Section 11.4 Objectives: 10. Define the terms haploid and diploid. Relate the terms to the life cycle of plants and animals. 11. Describe the process of meiosis. 12. Explain what is happening in each stage of meiosis 13. Use the chromosome theory to contrast between “linked” genes and those inherited by independent assortment 14. Compare and contrast mitosis and meiosis

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