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More Genetics & Pedigrees

More Genetics & Pedigrees. Incomplete Dominance. Multiple Alleles & Codominance. Additive effect of multiple genes on a single phenotype Results in normal distribution Examples: skin color, height. Polygenic Traits. A gene at one locus alters the expression of a gene at another locus.

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More Genetics & Pedigrees

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  1. More Genetics & Pedigrees

  2. Incomplete Dominance

  3. Multiple Alleles & Codominance

  4. Additive effect of multiple genes on a single phenotype Results in normal distribution Examples: skin color, height Polygenic Traits

  5. A gene at one locus alters the expression of a gene at another locus. Example: Black coat (B) is dominant to brown (b) Pigment color (C) is dominant to no pigment color (c) Epistasis

  6. Effect of Environment on Phenotype Less acidic soil More acidic soil

  7. Pleiotropic Effects

  8. Pedigree Male Female Heterozygous Shows trait

  9. Recessive characteristics • Inheritance pattern • Trait tends to skip generations

  10. Aa aa Child will have recessive trait? aa Probabilities Chance of “a” allele from mom? Chance of “a” allele from dad? Total x 1 = 1/2 1/2 1/2 2/2 (1)

  11. Dominant characteristics • Trait does not skip generations • Occurs frequently within a family

  12. Pedigree Analysis

  13. Sex linked characteristics • Tend to occur more in males than in females • Color-blindness • Hemophilia

  14. XCy Xcy XCXC XCXc XcXc 92% (0.92)(0.92) = 85% 8% 2x (0.92)(0.08) = 15% (0.08)(0.08) = 0.64% X-linked Recessives: More commonly seen in Males • Why? • Males only need one recessive allele to see trait. • E.g. Color-blindness • XC – 92 % of alleles • Xc – 8 % of alleles

  15. A woman with normal vision whose father was color-blind marries a color-blind male. What percent of the couple’s sons will be color-blind? • All • 75% • 50% • 25%

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