ChiSquares, Pedigrees, and Polygenic Traits

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Chi-Squares, Pedigrees, and Polygenic Traits
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I. Chi-Square

• A chi-square test (goodness of fit) is a test
  used to validate a hypothesis
• For our purposes, it will be used to determine if
  the results of a cross obey Mendels law or not
• To use chi-square the obtained values are
  compared to the expected values and a chi-square
  value (X2) are obtained

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II. Pedigrees

• A pedigree chart is used for analyzing and
  studying the inheritance of characteristics in a
  family
• In some cases the genotype of a person can be
  deduced as well as the inheritance pattern that
  the allele takes
• Genetic counselors use them to advise potential
  parents
• When creating pedigrees, certain rules apply
• Squares represent males
• Circles represent females
• Colored means expression
• ½ colored indicates a carrier
• Lines are used to show relationships

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III. Polygenic Traits

• Some characteristics are controlled by more than
  one gene
• These traits are called polygenic and include
  color in pigs, skin color in humans, and the comb
  in chickens
• Chicken combs are a result of an interaction
  between two genes R and P
• Four phenotypes result from this interaction
• Single rrpp
• Walnut R_P_
• Pea rrP_
• Rose R_pp