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Chapter 11-3 Beyond Dominant and Recessive Alleles

Chapter 11-3 Beyond Dominant and Recessive Alleles. I. Not all alleles follow Mendel’s patterns of inheritance. A. There are 4 other patterns of inheritance. 1. Incomplete Dominance - Neither allele is dominant.

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Chapter 11-3 Beyond Dominant and Recessive Alleles

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  1. Chapter 11-3 Beyond Dominant and Recessive Alleles

  2. I. Not all alleles follow Mendel’s patterns of inheritance. A. There are 4 other patterns of inheritance

  3. 1. Incomplete Dominance- Neither allele is dominant. The heterozygous genotype results in a BLENDING of the two homozygous phenotypes Ex. Snapdragon flower color Genotype Phenotype rr -- Red ww -- White rw -- Pink

  4. Cross a red snapdragon with a pink snapdragon r r r r r r r w r w r w

  5. 2. Co-dominance- Both alleles are dominant The heterozygous genotype expresses both phenotypes at the same time.

  6. Ex. Horses coat color Genotype – Phenotype RR -- Red WW -- White RW -- Roan (red & white) Ex. Erminette chicken feathers Genotype – Phenotype BB -- Black WW --- White BW -- Black&White

  7. B B Cross a Black chicken with an Erminette Chicken B BB BB W W BW BW W RW RW R Cross a White horse with a Roan horse. WW WW W

  8. 3. Multiple Alleles - Genes that have more than 2 possible ALLELES a. Ex. Blood type in humans 1. There are 3 possible alleles: A, B or O GenotypesPhenotype AA or AO -- Type A BB or BO -- Type B AB (rare) -- Type AB OO (most common) -- Type O

  9. b. **Type O is the universal DONOR—someone with Type O blood can give to any other blood type c. *Type AB is the universal RECIEPIENT—person with AB can take blood of any type.

  10. Can a man with type B blood have a type A child? B B A B A B A A A B A B B O A A B A O A A B A O

  11. 4. Polygenic Traits- controlled by MANY GENES a.Ex. Skin color—controlled by 4 genes.(8 alleles) b.This is the reason there is such a large range of skin colors.

  12. c. Example: parakeets are also polygenic Phenotypes Genotypes Whitefeathers – bbyy Bluefeathers- BByy or Bbyy Yellow feathers- bbYY or bbYy Green feathers- BBYY or BbYy BBYy or BbYY

  13. Polygenic parakeet punnett square • Like a two trait cross F-O-I-L Cross a homozygous yellow parakeet with a homozygous yellow homozygous blue (parents and offspring should have 4 letters for genotype!!!) ___________ x _________ BbYy bY bbYY BY BbYY BY By bY by bY BbYy By bbYY bY bbYy by

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