NOTES – Complex Inheritance Patterns

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    14-Jan-2016

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NOTES Complex Inheritance Patterns. Most human traits have more than 2 or 3 forms. Types of inheritance that are more complex than simple dominance, incomplete dominance or codominance control these traits. Traits are controlled by 1 gene with more than 2 alleles - PowerPoint PPT Presentation

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NOTES Complex Inheritance PatternsMost human traits have more than 2 or 3 forms. Types of inheritance that are more complex than simple dominance, incomplete dominance or codominance control these traits.Multiple Allelic Inheritance (Multiple Alleles) Traits are controlled by 1 gene with more than 2 allelesEx. The ABO Blood Type System in HumansThe gene that controls ABO blood type has 3 alleles:A = Type A blood B = Type B blood o = Type O BloodAlleles A and B are codominant and allele o is recessiveThere are 6 possible genotypes and 4 possible phenotypes:A A or A o=Type A BloodB B or B o= Type B BloodAB=Type AB Bloodo o = Type O BloodBlood CellsThere are four basic Blood types: Type A with A antigens on the red cells and anti B antibodies in the plasma. Type B with B antigens on the red cells and anti A antibodies in the plasma. Type AB with both A and B antigens on the red cells and no blood type antibodies in the plasma. Type O with no antigens on the red cells and both anti A and anti B antibodies in the plasma Polygenic InheritanceTraits are controlled by more than 1 geneThere are many possible phenotypesEx. Skin color is controlled by at least 3 genes A = dark skina = light skinB = dark skinb = light skinC = dark skinc = light skinDifferences in skin color are largely due to differences in the amount of melanin, a dark pigment produced by skin cells.Each dark skin allele (A, B, C) codes for high melanin productionEach light skin allele (a, b, c) codes for low melanin productionEach dark skin allele (A, B, C) in the genotype adds a small but equal amount of pigment to the skinSome possible genotypes and phenotypes:aabbcc=very light skin AABBCC=very dark skinAaBbCc= medium skin What would a Punnett Square for skin color look like?Cross two medium skin tone parentsAaBbCc X AaBbCcEach parent could produce 8 different possible combination to pass on: ABC, ABc, AbC, Abc, aBC, aBc, abC, or abcBlood Type Is PolygenicAnother level of specificity is added to blood type by examining the presence or absence of the Rh proteinEach blood type is either positive "+" (has the Rh protein) or negative "-" (no Rh protein) For example, a person whose blood type is "A positive" (A +), has both type A and Rh proteins on the surface of their red blood cells The Rh protein gene has two alleles:R = protein present (+) r = protein absent (-) Polygenic Blood TypeWhat is the phenotype of a person who has the blood type genotype ABRr?Type AB +What is the phenotype of a person who has the blood type genotype oorr?Type O What would be the genotype of a person who is A +AARR or AoRR or AARr or AoRr

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