Probability, Mendel, and Extensions to Mendel

Chi-square Test
• Are the observed data consistent with the data expected under the
hypothesis being tested?
Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings/Addison-Wesley
• χ 2 = Σ [(o-e) 2 / e] Values are significantly
different from expected
Dihybrid cross: Phenotypic ratio 9:3:3:1
• 9/16 dominant phenotypes at both genes
(A_B_)
• 3/16 dominant phenotype at first gene;
recessive phenotype at second gene
( A_bb)
• 3/16 recessive phenotype at first gene;
dominant phenotype at second gene
(aaB_)
• 1/16 recessive phenotypes at both genes
(aabb)
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