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Independent Assortment & Non-Mendelian Genetics

Independent Assortment & Non-Mendelian Genetics. EQ: What are the other outcomes of a cross?. Learning Goal - Genetics. 4 – I can predict the offspring of different crosses of parents and explain how the traits were inherited. I can apply monohybrid crosses to a dihybrid cross (Ex: RRYY x rryy)

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Independent Assortment & Non-Mendelian Genetics

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  1. Independent Assortment & Non-Mendelian Genetics EQ: What are the other outcomes of a cross?

  2. Learning Goal - Genetics 4 – I can predict the offspring of different crosses of parents and explain how the traits were inherited. I can apply monohybrid crosses to a dihybrid cross (Ex: RRYY x rryy) 3 – I can usually find the probability of the offspring and I understand meiosis 2 – I can do basic Punnett squares but still need help setting it up 1 – I need to review genetics

  3. phenotype: purple phenotype: white phenotype: purple I. Mendelian Genetics: A. Dominant & Recessive Review • One allele is DOMINANT over the other (because the dominant allele can “mask” the recessive allele) genotype: PP genotype: pp genotype: Pp

  4. PP Pp Pp pp Review Problem: A. Dominant & Recessive • In pea plants, purple flowers (P) are dominant over white flowers (p). Show the cross between two heterozygous plants. P p GENOTYPES: - PP (25%) Pp (50%) pp (25%) - ratio 1:2:1 P p PHENOTYPES: - purple (75%) white (25%) - ratio 3:1

  5. B. Two Cross/Dihybrid Cross • Mendel wondered if one allele for one gene would influence another allele for a separate gene • RRYY x rryy • (R) is round, (r) is wrinkled • (Y) is yellow, (y) is green • He found the two factor/dihybrid cross

  6. Example 1: F1 RRYY x rryy

  7. Example 2: F2 RrYy x RrYy

  8. 9:3:3:1

  9. What did Mendel find? In a two factor cross, the alleles would separate independently (not linked). Ratio for the F2 generation was 9:3:3:1

  10. Review Dihybrid Crosses Tall = TT Tall = Tt Short = tt Red = RR Red = Rr Yellow = rr • Cross two heterozygous plants for both traits.

  11. TtRr X TtRr

  12. TtRr X TtRr TR Tr tR tr TR TTRR TTRr TtRRTtRr Tr TTRr TTrrTtRrTtrr tR TtRR TtRr ttRR ttRr tr TtRr Ttrr ttRr ttrr

  13. TtRr X TtRr

  14. NNDD x NnDd

  15. II. Non-Mendelian Genetics • Incomplete Dominance • Codominance • Multiple Alleles • Polygenic Traits • Sex-Linked Traits

  16. RR = red rr = white Rr = pink A. Incomplete Dominance • a third (new) phenotype appears in the heterozygouscondition as a BLENDof the dominant and recessivephenotypes. • Ex - Dominant Red (R) + Recessive White (r) = Hybrid Pink (Rr)

  17. R R r r Rr Rr Rr Rr Example 3: Incomplete Dominance • Show the cross between a red and a white flower. GENOTYPES: - RR (0%) Rr (100%) rr (0%) - ratio 4:0 PHENOTYPES: • pink (100%); white (0%); red (0%)

  18. R r r r Rr Rr rr rr Example 4: Incomplete Dominance • Show the cross between a pink and a white flower. GENOTYPES: - RR (0%) Rr (50%) rr (50%) - ratio 1:1 PHENOTYPES: - pink (50%); white (50%) - ratio 1:1

  19. B. Codominance • in the heterozygous condition, both alleles are expressed equally with NO blending! Represented by using two DIFFERENT capital letters. • Example: • Dominant Black (B) + Dominant White (W) = • SpeckledBlack and White Phenotype (BW)

  20. Codominance Example: Speckled Chickens • BB = black feathers • WW = white feathers • BW = black & white speckled feathers • Notice – NO GRAY! NO BLEND! Each feather is either black or white

  21. Codominance Example 5: Rhodedendron • R = allele for red flowers • W = allele for white flowers • Cross a homozygous red flower with a homozygous white flower. • Note that it’s not blended or light pink

  22. Codominance Example:Roan cattle • cattle can be red (RR – all red hairs) white (WW – all white hairs) roan (RW – red and white hairs together)

  23. Codominance Example 6:Appaloosa horses • Gray horses (GG) are codominant to white horses (WW). The heterozygous horse (GW) is an Appaloosa (a white horse with gray spots). • Cross a white horse with an appaloosa horse. W W G W GW GW WW WW

  24. NS = some of each SS = sickle cells NN = normal cells Codominance Example #7 • Sickle Cell Anemia – blood disorder commonly found in Africans (1 in 500) sick

  25. NS SS SS NS Example 7: Sickle Cell Codominance • Show the cross between an individual with sickle-cell anemia and another who is a carrier but not sick. N S GENOTYPES: - NS (50%) SS (50%) - ratio 1:1 S S PHENOTYPES: - carrier (50%) sick (50%) - ratio 1:1

  26. C. Multiple Alleles • there are more than twoalleles for a gene. • Ex – blood type consists of two dominant and one recessive allele options. • Allele A & B are dominant over Allele O (i)

  27. Multiple Alleles:Blood Types (A, B, AB, O) • Rules for Blood Types: A and B are co-dominant (Both show) AA or IAIA = type A BB or IBIB = type B AB or IAIB = type AB A and B are dominant over O (Regular dom/rec) AO or IAi = type A BO or IBi = type B OO or ii = type O

  28. Multiple Alleles:Blood Types (A, B, AB, O)

  29. Ai Ai Bi Bi Example 8: Multiple Alleles • Show the cross between a mother who has type O blood and a father who has type AB blood. GENOTYPES: i i - Ai (50%) Bi (50%) - ratio 1:1 A B PHENOTYPES: - type A (50%) type B (50%) - ratio 1:1

  30. Bi AB Ai ii Example 9: Multiple Alleles • Show the cross between a mother who is heterozygous for type B blood and a father who is heterozygous for type A blood. GENOTYPES: A i • AB (25%); Bi (25%); • Ai (25%); ii (25%) • - ratio 1:1:1:1 B i PHENOTYPES: • type AB (25%); type B (25%) • type A (25%); type O (25%) • - ratio 1:1:1:1

  31. Multiple Alleles:Lab Mouse Fur Colors • Fur colors (determined by 4 alleles): black agouti yellow & (white)

  32. Multiple Alleles:Rabbit Fur Colors • Fur colors (determined by 4 alleles): full, chinchilla, himalayan, albino

  33. D. Polygenic Traits • traits produced by multiple genes • example: skin color, tallness, eye color

  34. E. Sex-Linked Traits • Gene is attached to the X chromosome only, not found on the Y chromosome at all. • (women have XX, men have XY chromosomes). These disorders are more common in boys. • Examples: • red-green colorblindness • Hemophilia • baldness

  35. Sex-Linked Traits • in males, there is no second X chromosome to “mask” a recessive gene. If they get an X with the disorder, they have it. Girls must inherit defective X’s from both parents.

  36. Sex-Linked Traits A: 29, B: 45, C: --, D: 26  Normal vision A: 70, B: --, C: 5, D: --  Red-green color blind A: 70, B: --, C: 5, D: 6  Red color blind A: 70, B: --, C: 5, D: 2  Green color blind

  37. Chromosomal Disorders • When too many/few chromosomes produced from meiosis

  38. Trisomy 21 – Down Syndrome

  39. Other Chromosomal Abnormalities • http://learn.genetics.utah.edu/content/disorders/chromosomal/

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