Complex Patterns of Inheritance

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Complex Patterns of Inheritance
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Simple Inheritance

• Mendel studied simple patterns of inheritance.
• Found that inheritance was controlled by a
  dominant allele (B) or recessive allele (b).
• However, there are many inheritance patterns that
  are more complex.
• Most traits arent simply dominant or recessive.

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• Heterozygous Homozygous dominant individuals
  both have the same phenotype.
• Example --- Brown eyes Dominant (B) Blue eyes
  Recessive (b)
• Individual with BB or Bb have what color eyes?
  Brown

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Incomplete Dominance

• When traits are inherited in an incomplete
  dominance pattern, the phenotype of the
  heterozygous (Bb) is between the pure dominant
  (BB) and the pure recessive (bb).

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Codominance

• Codominant alleles --- Both alleles are expressed
  equally.
• Example --- when a certain variety of black
  chicken is crossed with a white chicken, all
  offspring are checkered (black white).
• Both feather colors are produced by codominant
  alleles.

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Multiple Alleles

• Multiple alleles --- traits controlled by more
  than 2 alleles.
• Example of a trait controlled by multiple alleles
  is blood type.

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