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Gene Interactions

Gene Interactions. Simple Dominance The heterozygous expresses the dominant phenotype 1 gene 2 alleles 2 phenotypes Incomplete Dominance The heterozygous expresses less than the homozygous dominant individual so it seems incomplete 1 gene 2 alleles 3 phenotypes Codominance

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Gene Interactions

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  1. Gene Interactions • Simple Dominance • The heterozygous expresses the dominant phenotype • 1 gene • 2 alleles • 2 phenotypes • Incomplete Dominance • The heterozygous expresses less than the homozygous dominant individual so it seems incomplete • 1 gene • 2 alleles • 3 phenotypes • Codominance • The heterozygous expresses both dominant alleles • 1 gene • 2 dominant alleles • 3 phenotypes

  2. Gene Interactions • Multiple alleles • 3 or more alleles interact to give different phenotypes of the same gene • 1 gene • 3 or more alleles • Multiple phenotypes • Blood typing • Polygeneic • 2 or more genes interact to give a wide range of different phenotypes • 2 or more genes • 2 alleles • Multiple variations of phenotypes • Hair and eye color • Epistasis • A gene controls the expression of a different gene • Rooster combs • Black, Chocolate, Yellow labs

  3. Human Blood Typing (ABO) • Presence or absence of AB antigens • Type A – A antigen • IAIA or IAi • Type B – B antigen • IBIB or IBi • Type AB – Both A and B antigen • IAIB • Type O – none of the antigens • ii • Because antigens are recognized by the immune system the right blood must be used for transfusions • Wrong blood = the immune system will attack it • AB = receive any blood AB = donate to AB only • O = receive only O O = donate to anyone • RH factors • Simple dominance (not the whole story but for our sake) • Have Rh antigen = + (dominant) • Don’t have Rh antigen = – (recessive) • Immune system during pregnancy

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