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Complex Genetics

Complex Genetics. When Mendel ’ s rules don ’ t exactly apply…especially in human traits!. Incomplete Dominance. Medium Phenotype When the heterozygote is in between the recessive and dominant. Problem.

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Complex Genetics

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  1. Complex Genetics When Mendel’s rules don’t exactly apply…especially in human traits!

  2. Incomplete Dominance • Medium Phenotype • When the heterozygote is in between the recessive and dominant.

  3. Problem • A red 4 o’clock is crossed a pink 4 o’clock. What are % of the genotypes and phenotypes of the offspring.

  4. Codominance • When both phenotypes are expressed. • Use capital letters to represent both genes.

  5. Problem • A black cow is mated with a white cow. Both black and white are dominant. What will be the phenotype of the offspring. Show a Punnett Square.

  6. Multiple Alleles • When there is more than one allele for a gene. • Blood type • I is dominant • i is recessive • I can be IA or IB

  7. Problem • A mother is Blood type A. The father is blood type B. What is their genotypes if they have a child who is blood type O? • A: • B: • O: Punnett Squares to show answer:

  8. Getting Blood!

  9. Blood Types

  10. Sex Linked • When a gene is on the female X chromosome. • Females get two copies, males only get one. • If males have a mutant recessive, they will have the disease.

  11. Example: Colorblindness • Rods--Black and White vision • Cones--Color Vision • Gene for cones on X chromosome • XBXB; XBXb-Normal Female • XbXb-Colorblind Female • XBY-Normal Male • XbY-Colorblind Male

  12. Problem • A man is normal vision. His wife is normal vision but her mom was colorblind. What is the chance of their daughters being colorblind? Their sons? Show in a Punnett Square in proper notation.

  13. Polygenic Inheritance • Many genes affect a phenotype. Most visual traits have a range. • Ex. Eye color, hair color, height

  14. Problem • Skin color is influenced by 3 major genes. Dominant genes cause greater production of melanin. • Which of the following would be the genotype for a darker skin phenotype? • AABbcc • Aabbcc • AaBbCC

  15. Pleiotropy • One mutation has many effects • Example--Cystic Fibrosis • What type of mutation? • What are two organ systems that it effects? • Could there be an evolutionary significance to the CF allele?

  16. Epistasis • When one gene effects the outcome of another gene. • B_E_ : Black fur and black skin • B_ee: Yellow fur and black skin • bbE_: Brown fur and brown skin • Bbee: Yellow fur; brown skin • What does each trait code for? • How does the skin trait affect fur color?

  17. Review: Dihybrid cross • How is a dihybrid cross different than a four box Punnett Square? • How does the dihybrid Cross show Mendel’s Law of Segregation? • Law of Indepdent Assortment? • Random Fertilization?

  18. Practice Makes Perfect! • Mendelian’s Law of Dominance • Make your own 5 problems and answer • Non-Mendelian Genetics • Worksheets • Corn Lab • Lab Notebook!

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