Ch.14 genetics

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Ch.14 genetics

  1. 1. Genetics Chapter 14
  2. 2. Gregor Mendel• Father of Genetics• Used peas to study heredity
  3. 3. Vocabulary• Heredity: passing of traits from parent to offspring• Genetics: study of heredity• True-breeding: self-pollinating plant always produces the same offspring• Allele: alternative versions of a gene
  4. 4. More Vocabulary• Dominant: A• Recessive: a• Homozygous: AA or aa• Heterozygous: Aa
  5. 5. Law of Segregation• Separation of alleles into separate gametes• 50% chance that one allele will go into a gamete
  6. 6. Test Cross
  7. 7. Law of Independent Assortment
  8. 8. Incomplete Dominance
  9. 9. Multiple Alleles
  10. 10. Epistasis• 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)
  11. 11. Polygenic Traits• Additive effect of multiple genes on a single phenotype• Results in normal distribution• Examples: skin color, height
  12. 12. Effect of Environment on Phenotype More acidic soil Less acidic soil
  13. 13. Pleiotropic Effects
  14. 14. Pedigree Analysis
  15. 15. Pedigree Male Female Heterozygous Shows trait
  16. 16. Probabilities Child will have Aa aa recessive trait? aa Chance of “a” Chance of “a”allele from dad? allele from mom? Total 1 /2 2 /2 (1) 1 /2 x 1 = 1/2
  17. 17. Recessive characteristics Inheritance pattern •Trait tends to skip generations
  18. 18. Dominant characteristics •Trait does not skip generations •Occurs frequently within a family
  19. 19. Sex linked characteristics •Tend to occur more in males than in females •Color-blindness •Hemophilia
  20. 20. 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 Female Males s XCXC (0.92)(0.92) = 85% XCy 92% XCXc 2x (0.92)(0.08) = 15% Xcy 8% XcXc (0.08)(0.08) = 0.64%
  21. 21. Problem: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? 1. All 2. 75% 3. 50% 4. 25%

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