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Patterns of Heredity

Patterns of Heredity. Many inherited traits are much more complex then the simple Mendelian rules. - Most genes are not simply dominant or recessive . Incomplete Dominance = . the phenotype of the heterozygous form is a mix of the dominant and recessive genes.

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Patterns of Heredity

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  1. Patterns of Heredity

  2. Many inherited traits are much more complex then the simple Mendelian rules. - Most genes are not simply dominant or recessive.

  3. Incomplete Dominance = • the phenotype of the heterozygous form is a mix of the dominant and recessive genes. (a third phenotype is produced)

  4. Ex: A cross between a red flower (RR) and white flower (rr) produces a pink flower (Rr).

  5. Practice Problem • When a mouse with black fur is crossed with a mouse with white fur, all first generation offspring have gray fur. What genotypic and phenotypic ratios will be expected in the next generation?

  6. What are the genotypes? • Black = Dominant = BB • White = Recessive = bb • Gray = Incomplete Dom. = Bb • BB x bb = All BbB B b b

  7. Set up the next generation cross • Bb (gray) x Bb (gray) B b B b

  8. Genotypic & Phenotypic ratio • 1 BB: 2 Bb : 1 bb • 25% Black • 50% Gray • 25% White

  9. Codominance = • the phenotype of the heterozygous form expresses two dominant genes equally. • Ex: Blood type AB

  10. Practice Problem A woman with type AB blood has a child with a man with type AB blood. What type of blood will their children have?

  11. Set up Punnett Square A B A B

  12. Genotypic & Phenotypic Ratios • 1 AA: 2 AB: 1 BB • 25% A Blood Type • 50% AB Blood Type • 25% B Blood Type

  13. Multiple Alleles = • traits with three or more genes (letters). However, only two of these genes are passed on to the offspring. • Ex: Blood type – A, B, O • There are 4 different types of blood types: • A, B, AB, and O • Type O is recessive to both A and B

  14. Blood Types • Phenotype A Blood Type • Genotypes AA or Ao • Phenotype B Blood Type • Genotypes BB or Bo • Phenotype AB Blood Type • Genotype AB only • Phenotype O Blood Type • Genotype oo only

  15. Blood Types – Practice Problems A woman with type O blood type has a baby with a man with type AB blood type. What blood type can their child have?

  16. Set up Punnett Square O O A B

  17. Genotypic & Phenotypic Ratios • 2 Ao: 2 Bo • 50% Ao (Type A) • 50% Bo (Type B)

  18. Blood Types – Practice Problems A woman with type AA blood type has a baby with a man with type Bo blood type. Can they have a child with type O blood?

  19. Set up Punnett Square B O A A

  20. Genotypic & Phenotypic Ratios • 2 AB: 2 Ao • 50% AB (Type AB) • 50% Ao (Type A) No, they could not have a child with O blood type – no oo.

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