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Complex Patterns of Inheritance

Complex Patterns of Inheritance. I. Incomplete Dominance. An individual displays a trait that is intermediate between the two parents Example: a red snapdragon crossed with a white snapdragon produces pink offspring. Red = RR, White = WW, Pink = RW.

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Complex Patterns of Inheritance

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  1. Complex Patterns of Inheritance

  2. I. Incomplete Dominance • An individual displays a trait that is intermediate between the two parents • Example: a red snapdragon crossed with a white snapdragon produces pink offspring

  3. Red = RR, White = WW, Pink = RW

  4. Make a Punnett square for a red plant crossed with a white plant R R W W

  5. All offspring are pink, with RW genotype R R W W

  6. Show the cross between two pink snapdragons

  7. Offspring are 1 red, 2 pink, and 1 white R W R W

  8. Incomplete dominance in horse coat color

  9. II. Codominance • Two dominant alleles are expressed at the same time • Roan coat color in horses or cows is an example • A roan horse has both red and white hairs

  10. Roan  has red and white hairs

  11. Parents  Codominance in chicken feather color. Black and White feathers 

  12. III. Multiple Alleles • Traits controlled by more than 2 alleles. • Examples are pigeon feather colors and fur color in many animals.

  13. Coat color in rabbits

  14. List all possible genotypes for a: a) dark gray-coated rabbit CC, Ccch, Cch, Cc b)chinchilla rabbit cchcch, cchch, cchc c) Himalayan rabbit chch, chc d) white rabbit cc

  15. Predict the phenotype for a rabbit with a chcch genotype chinchilla Predict the phenotype for a rabbit with a Cch genotype dark gray • Would it be possible to obtain white rabbits if one parent is white and the other is chinchilla? Yes, if the chinchilla parent has a white allele

  16. Would it be possible to obtain chinchilla rabbits if one parent is Himalayan and the other is white? No, because chinchilla is dominant to both Himalayan and white, so the allele couldn’t be “hiding”. • A chinchilla rabbit is mated with a Himalayan. Some offspring are white. What are the parents’ genotypes? Chinchilla is cchc and Himalayan is chc .

  17. IV. Sex-linked traits • A sex-linked trait is a trait whose allele is located on either the X or Y chromosome.

  18. A) Hairy Ears are caused by a gene on the Y Chromosome

  19. B) Most sex-linked traits on X chromosome are recessive • Examples include: hemophilia, red-green colorblindness, and a form of muscular dystrophy

  20. People with red-green color blindness see the number 35, while people with normal vision see the number 57

  21. Hemophilia • A disorder in which the blood does not clot properly • Sex-linked recessive (on the X chromosome) • Males receive the hemophilia gene from their mothers Extensive bruising of the left forearm and hand in a patient with hemophilia.

  22. Genotypes for females XHXH = normal blood clotting, non-carrier XHXh = normal blood clotting, carrier of gene XhXh = female with hemophilia Queen Victoria of the United Kingdom was a carrier of hemophilia

  23. Genotypes for Males • XHY = normal blood clotting • XhY = male with hemophilia • Tsarevich Alexei of Russia had hemophilia

  24. What is Alix’s genotype?

  25. 1. Cross a carrier mother with a normal father.

  26. What percent of sons have hemophilia?What percent of daughters have hemophilia?

  27. 50% of sons have hemophilia, 0% of daughters have hemophilia.

  28. 2. Cross a hemophiliac father with a normal (non-carrier) mother.

  29. What percent of sons have hemophilia? What percent of daughters are carriers?

  30. 0% percent of sons have hemophilia. 100% percent of daughters are carriers.

  31. 3. Cross a carrier mother with a hemophiliac father.

  32. What percent of sons have hemophilia?What percent of daughters have hemophilia?

  33. 50% percent of sons have hemophilia. 50% percent of daughters have hemophilia.

  34. Cross a hemophiliac mother with a normal father • What percent of sons have hemophilia? • What percent of daughters have hemophilia?

  35. 100% percent of sons have hemophilia. 0% percent of daughters have hemophilia.

  36. V. Polygenic traits • Traits that are influenced by 2 or more genes • Examples include human height, weight, hair color, eye color, and skin color

  37. Coat color in Labrador retrievers

  38. Coat color in Labrador retrievers

  39. Is it possible for two chocolate lab parents to have black lab offspring?

  40. VI. Traits influenced by the environment. • Color of hydrangea flowers (blue in acidic soil, pink in basic soil)

  41. Color of arctic fox • Human height, skin color, behavior

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