1 / 51

Mendelian Exceptions

Mendelian Exceptions. 1.31.13. Mendelian Exceptions. Mendel got lucky – all 7 traits he studied showed complete (simple) dominance . Mendelian Exceptions. Mendel got lucky – all 7 traits he studied showed complete (simple) dominance .

aldis
Download Presentation

Mendelian Exceptions

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Mendelian Exceptions 1.31.13

  2. Mendelian Exceptions Mendel got lucky – all 7 traits he studied showed complete (simple) dominance.

  3. Mendelian Exceptions • Mendel got lucky – all 7 traits he studied showed complete (simple) dominance. • One allele is completely dominant over the other allele • Homozygous dominant and heterozygous = same phenotype • 1 allele is enough for full expression of dominant trait

  4. Incomplete Dominance = the norm Heterozygote = intermediate phenotype 1 allele is not enough for full expression

  5. Incomplete Dominance • Ex: flower color • R = red RR xrr • r = white

  6. Incomplete Dominance F2: RrxRr

  7. Incomplete Dominance Rr 1 red 2 pink 1 white Rr Rr Rr F2: RrxRr Alleles not blended – still able to separate.

  8. Codominance – Both alleles are expressed equally

  9. Codominance – Both alleles are expressed equally • Ex: Cows • B = black • W = white • BB = Black • WW = White • BW = ???

  10. Codominance – Both alleles are expressed equally • Ex: Cows • B = black • W = white • BB = Black • WW = White • BW = Black and white • Other examples: calico cats, zebras, streaked flowers…

  11. Multiple alleles • Allele: Alternate forms of a gene • Only 2 possible alleles in an individual, BUT any # of alleles may be present in a population due to mutations

  12. Blood Types (ABO blood types) Example of simple dominance, codominance, and multiple alleles

  13. Blood Types (ABO blood types) • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  14. Blood Types (ABO blood types) Genotype Phenotype AA • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  15. Blood Types (ABO blood types) Genotype Phenotype AA A • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  16. Blood Types (ABO blood types) Genotype Phenotype AA A AO • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  17. Blood Types (ABO blood types) Genotype Phenotype AA A AO A • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  18. Blood Types (ABO blood types) Genotype Phenotype AA A AO A BB • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  19. Blood Types (ABO blood types) Genotype Phenotype AA A AO A BB B • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  20. Blood Types (ABO blood types) Genotype Phenotype AA A AO A BB B BO • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  21. Blood Types (ABO blood types) Genotype Phenotype AA A AO A BB B BO B • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  22. Blood Types (ABO blood types) Genotype Phenotype AA A AO A BB B BO B AB • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  23. Blood Types (ABO blood types) Genotype Phenotype AA A AO A BB B BO B AB AB (codom.) • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  24. Blood Types (ABO blood types) Genotype Phenotype AA A AO A BB B BO B AB AB (codom.) OO • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  25. Blood Types (ABO blood types) Genotype Phenotype AA A AO A BB B BO B AB AB (codom.) OO O • Example of simple dominance, codominance, and multiple alleles • Alelles = A, B, O • A & B = Dominant • O = Recessive

  26. Q: What combination of parents have an equal chance of having any of the 4 blood types?

  27. Q: What combination of parents have an equal chance of having any of the 4 blood types?

  28. Mexican Hairless Dogs • Hairless (H) is completely dominant over hairy (h). • When two hairless are crossed: • 2/3 hairless • 1/3 hairy Why???

  29. Mexican Hairless Dogs • Hairless (H) is completely dominant over hairy (h). • When two hairless are crossed: • 2/3 hairless • 1/3 hairy

  30. Lethal Allele 2 copies of a lethal allele = death (usually stillborn) Hint: if offspring ratio is x/3, think lethal allele (someone is dying)

  31. Lethal Allele Q: How can we breed hairless dogs without stillborns?

  32. 3, 4, 5, etc. trait crosses If a pea plant that is TTRrPp is crossed with a plant that is TtrrPp, what percent of the offspring will be heterozygous for all three traits?

  33. If a pea plant that is TTRrPp is crossed with a plant that is TtrrPp, what percent of the offspring will be heterozygous for all three traits? Is there an easier way???

  34. Product Rule Make a simple 4 square cross for each trait, then multiply the results for each

  35. Epistasis • The process of one gene controlling the expression of another • An epistatic gene can completely mask the effects of another gene • 2 genes -> 1 trait

  36. Example: Hair Color • 2 genes are responsible for hair color: • black-brown gene • red-blonde gene

  37. Example: Hair Color • 2 genes are responsible for hair color: • black-brown gene • red-blonde gene • Black-brown is epistatic(dominant) over the red-blonde gene • Two “exceptions” present – incomplete dominance and epistasis

  38. -> controls -> • R = red • r = blonde • B = black • b = brown

  39. -> controls -> • R = red • r = blonde • B = black • b = brown • BB__ =

  40. -> controls -> • R = red • r = blonde • B = black • b = brown • BB__ = black

  41. -> controls -> • R = red • r = blonde • B = black • b = brown • BB__ = black • Bbrr =

  42. -> controls -> • R = red • r = blonde • B = black • b = brown • BB__ = black • Bbrr = brown

  43. -> controls -> • R = red • r = blonde • B = black • b = brown • BB__ = black • Bbrr = brown • BbR_ =

  44. -> controls -> • R = red • r = blonde • B = black • b = brown • BB__ = black • Bbrr = brown • BbR_ = auburn

  45. -> controls -> • R = red • r = blonde • bbRR = • B = black • b = brown • BB__ = black • Bbrr = brown • BbR_ = auburn

  46. -> controls -> • R = red • r = blonde • bbRR = red • B = black • b = brown • BB__ = black • Bbrr = brown • BbR_ = auburn

  47. -> controls -> • R = red • r = blonde • bbRR = red • bbRr = • B = black • b = brown • BB__ = black • Bbrr = brown • BbR_ = auburn

  48. -> controls -> • R = red • r = blonde • bbRR = red • bbRr = strawberry blonde • B = black • b = brown • BB__ = black • Bbrr = brown • BbR_ = auburn

  49. -> controls -> • R = red • r = blonde • bbRR = red • bbRr = strawberry blonde • bbrr = • B = black • b = brown • BB__ = black • Bbrr = brown • BbR_ = auburn

  50. -> controls -> • R = red • r = blonde • bbRR = red • bbRr = strawberry blonde • bbrr = blonde • B = black • b = brown • BB__ = black • Bbrr = brown • BbR_ = auburn

More Related