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POST MENDELIAN GENETICS

POST MENDELIAN GENETICS. EXTENSION OF MENDEL’S RULES. Phenotypic variation is not always due to simple dominance/recessive-ness of genes. EXTENSION OF MENDEL’S RULES. Some Traits Deviate from Mendelian Patterns: Incomplete Dominance: Co Dominance: Environmental Effects:

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POST MENDELIAN GENETICS

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  1. POST MENDELIAN GENETICS

  2. EXTENSION OF MENDEL’S RULES • Phenotypic variation is not always due to simple dominance/recessive-ness of genes

  3. EXTENSION OF MENDEL’S RULES Some Traits Deviate from Mendelian Patterns: • Incomplete Dominance: • Co Dominance: • Environmental Effects: • Quantitative Traits:

  4. INCOMPLETE DOMINANCE • No Allele Is Completely Dominant

  5. Incomplete dominance in Snapdragon flower color Parental generation X RR rr F1 generation: All Heterozygotes Rr Self-fertilization F2 generation 1/4 RR 1/4 Rr 1/4 Rr 1/4 rr Red Pink White

  6. INCOMPLETE DOMINANCE • Red allele = red pigment • White allele = no pigment • In heterozygous form

  7. CODOMINANCE • Two alleles specify different phenotypes, but…

  8. CODOMINANCE Blood type: • Determined by type of carbohydrate on RBC membrane • 3 possible alleles:

  9. CODOMINANCE Blood Type: • With alleles: AA or AO, you have • With alleles: BB or BO, you have • With alleles: OO, you have • With alleles: AB, you have

  10. CODOMINANCE • ABO Blood System:

  11. CODOMINANCE • Our immune system produced proteins (“antibodies”) that recognize foreign carbohydrates and causes foreign cells to clump together • A Blood has • B Blood has • O Blood has

  12. ENVIRONMENTAL EFFECTS • Environmental conditions help determine expression of genotype • Ex:

  13. ENVIRONMENTAL EFFECTS • Temp. sensitive enzyme acts at surface of body:

  14. QUANTITIVE TRAITS A result of more than one gene contributing to phenotype Polygenetic Inheritance:

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