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11-3 Exploring Mendelian Genetics

11-3 Exploring Mendelian Genetics. Key Concepts: What is the principle of independent assortment? What inheritance patterns exist aside from simple dominance? Vocabulary: Independent assortment Incomplete dominance Codominance Multiple alleles Polygenic traits.

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11-3 Exploring Mendelian Genetics

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  1. 11-3 Exploring Mendelian Genetics • Key Concepts: • What is the principle of independent assortment? • What inheritance patterns exist aside from simple dominance? • Vocabulary: • Independent assortment • Incomplete dominance • Codominance • Multiple alleles • Polygenic traits

  2. Two-Factor (Two-Gene) Cross • Why is this called a two factor cross? Because the experiment tests two characteristics controlled by two genes. • Mendel’s Experiment: Two-factor cross • Mendel crossed two homozygous plants (Pgen) • He looked at two genes (seed shape and seed color) • Pgeneration: Round&Yellowx Wrinkled &Green • F1 offspring produced…? • F1 generation: AllRoundYellow peas • Which alleles are dominant? Round shape and Yellow color.

  3. SummarizationMendel’s two factor cross • Mendel crossed plants that were homozygous dominant for round yellow peas (RRYY) and plants that were homozygous recessive for wrinkled green peas (rryy). • All of the F1 offspring were heterozygous dominant for round yellow peas (RrYy).

  4. In a monohybrid cross . . . If the genotype of a plant is Tt, each parent can only pass on one allele per gene in their gametes. (gene = height) Tt T or t

  5. For a dihybrid cross . . . If the genotype of a plant is TtYy, each parent can STILL only pass on one allele for each gene in their gametes.(gene= height and leaf shape) TtYy TY or tY or Ty or ty

  6. Principle of Independent Assortment • States that genes for different traits can segregate independently during the formation of gametes (meiosis). • If the genotype of a plant is TtYy (T= gene for height; Y= gene for leaf shape), what are the four possible combinationsof gametes? • how do you figure out the gametes?

  7. How do you figure out the possible gametes? Remember FOIL (from math???— the distributive property) T t Y y The gametes mom will produce: F = First O = Outside I = Inside L = Last Ex: Mom’s genotype TY, Ty, tY, ty

  8. Independent Assortment..in other words… • Does the segregation of one pair of alleles affect the segregation of another pair of alleles? • EX: does the gene that determines seed shape have anything to do with the gene that determines seed color? • The answer: NO • If genes are not connected, then they should separate (segregate) independently: Independent Assortment

  9. P generation F1 generation • If you wanted to cross the offspring of the F1 generation… • What would the gametes be? (use FOIL) • SsYy= SY, sY, Sy, sy • SsYy= SY, sY, Sy, sy • NEXT—try the cross to get the F2 generation!!!

  10. SsYy x SsYy SY SysY sy SY Sy sY sy

  11. SsYy x SsYy SY SysY sy SY Sy sY sy

  12. Independent Assortment • The alleles for seed shape segregated independently of the alleles for seed color. • This phenomenon is known as… • Independent assortment (the 2 genes are on different chromosomes.)

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