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Mendel’s Legacy

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Mendel’s Legacy. Chapter 9-1. Objectives. Describe Mendel’s Law of Segregation and Independent Assortment through patterns of inheritance Use Punnett squares to determine probablility of genotype and phenotype Draw monohybrid and dihybrid crosses. Vocabulary. Allele Codominance

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Mendel’s Legacy

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  1. Mendel’s Legacy Chapter 9-1

  2. Objectives • Describe Mendel’s Law of Segregation and Independent Assortment through patterns of inheritance • Use Punnett squares to determine probablility of genotype and phenotype • Draw monohybrid and dihybrid crosses

  3. Vocabulary • Allele • Codominance • Complete Dominance • Dihybrid cross • Dominant • Genetics • Genotype • Heredity • Heterozygous • Homozygous • Incomplete dominance • Law of Independent assortment • Law of segregation • Monohybrid cross • Phenotype • Probability • Punnett square • Pure • Recessive • Strain • Trait

  4. Mendel • Heredity is the transmission of characteristics from parents to offspring • Observed 7 traits (characteristics) of pea plants and wanted to explain variations • Controlled pollination (pollen from male anther transferred to female stigma) • Self-pollination pollinates same flower or same plant • Cross-pollination pollinates another plant

  5. Experiments • Created 14 strains (pure [always produce offspring with trait] for specific trait) P1 generations (parent) • Created an F1 generation of cross-pollinated plants of a specific strain • Created an F2 generation of self-pollinated plants • Counted and recorded traits in every cross

  6. Results and Conclusions • Concluded that 1 factor in a pair may prevent other from having an effect • Dominant factor masks other factor • Recessive factor didn’t appear in F1 but reappears • Law of segregation states that factors are separated in gametes (1 trait) • Law of independent assortment states that factors for different characteristics are distributed individually (more than 1 trait)

  7. Chromosomes and Genes • Molecular genetics studies the structure and function of chromosomes and genes • Factors are called alleles • Dominant (capital letter) recessive (lowercase letter) • Offspring receives 1 allele from each parent • Law of independent assortment is supported because chromosomes separate independently

  8. Genetic Crosses Chapter 9-2

  9. Genotype and Phenotype • Genotype is the genetic makeup • White, pp Purple, PP or Pp • Phenotype is the appearance • Homozygous is when both alleles are the same (pp or PP) • Heterozygous is when alleles are different (Pp)

  10. Probability • The likelihood an event will occur • Decimal, percent, or fraction • Probability= (number of times an event is expected)/(number of opportunities)

  11. Predicting Results of Monohybrid Crosses • Monohybrid cross is a cross between individuals involving one pair of traits • A Punnett Square aids in predicting probability inherited by offspring • Genotypic ratio is the ratio of genotypes • Phenotypic ratio is the ratio of phenotypes • A testcross is when an unknown genotype is crossed with homozygous recessive

  12. Homozygous x Homozygous Homozygous x Heterozygous Testcross Heterozygous x Heterozygous

  13. Predicting Results of Monohybrid Crosses • Complete dominance heterozygous and homozygous dominant look the same • Incomplete dominance is when both alleles (heterozygous) influence appearance • Ex: Red allele and white allele make pink • Codominance is when both alleles (heterozygous) are expressed but do not blend • Ex: Brown and black coat on dog

  14. Incomplete Dominance Codominance

  15. Predicting Results of Dihybrid Crosses • Dihybrid cross is between two pairs of different traits Homozygous x Homozygous Heterozygous x Heterozygous

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