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Genetics 2 ruder


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Genetics 2 ruder

  1. 1. Patterns of Inheritance Complete Dominance Incomplete Dominance Codominance Sex-Linked Inheritance
  2. 2. Complete Dominance <ul><li>You know this! </li></ul><ul><li>Dominant – completely masks recessive </li></ul><ul><li>Dominant – represented by C apital letter. </li></ul><ul><li>Recessive – represented by lower c ase. </li></ul><ul><li>Genotypes: BB – homozygous dominant </li></ul><ul><li>Bb- heterozygous (dom.) </li></ul><ul><li>bb – homozygous recessive </li></ul><ul><li>bb only way recessive trait can be expressed! </li></ul>
  3. 3. BB Bb bb Brown Brown Blue
  4. 4. Practice!!! <ul><li>Draw a Punnett Square to show the cross between a male cat heterozygous for having a tail with a female cat homozygous recessive for no tail. </li></ul><ul><li>Provide the genotypic and phenotypic results. </li></ul>
  5. 5. Check your answer! Tt x tt Tt Tt tt tt
  6. 6. Keep Checking! <ul><li>Genotypic Ratio: </li></ul><ul><li>TT – 0/4 , Tt – 2/4 , tt – 2/4 </li></ul><ul><li>Phenotypic Ratio: </li></ul><ul><li>Tail – 2/4 </li></ul><ul><li>No tail – 2/4 </li></ul>
  7. 7. Incomplete Dominance <ul><li>NEITHER allele completely masks the other. </li></ul><ul><li>Still use C apital and lower c ase letters. </li></ul><ul><li>Example: Carnations can be red, pink, or white. Use the letter C for color. </li></ul><ul><li>CC – red, Cc – pink, cc – white </li></ul><ul><li>Homozygous gives either extreme, heterozgyous give a “new” blend of the two. </li></ul>
  8. 8. CC Cc cc
  9. 9. Practice Incomplete Dominance! <ul><li>A breed of dog has hair texture that is determined by incompletely dominant traits. The hair t exture can be Straight (TT), Wavy (Tt), or Curly (tt). </li></ul><ul><li>Cross to wavy haired dogs and provide genotypic and phenotypic results. </li></ul>
  10. 10. Check your answers! TT Tt Tt tt
  11. 11. Genotypes and phenotypes <ul><li>Genotypes: Phenotypes: </li></ul><ul><li>¼ TT Straight Hair </li></ul><ul><li>2/4 Tt Wavy Hair </li></ul><ul><li>¼ tt Curly Hair </li></ul>
  12. 12. Codominance <ul><li>Both Alleles are EQUALLY dominant. </li></ul><ul><li>Still use C apital and lower c ase letters. </li></ul><ul><li>Example: A breed of horse has hair color that is controlled by codominant alleles. </li></ul><ul><li>The h air can be Red, White or an equal combination of both red and white hairs together. </li></ul><ul><li>HH – Red, Hh – both, hh – white. </li></ul>
  13. 13. Roan Horse
  14. 14. Another Example: Blood Type <ul><li>This can be confusing, pay attention!!! </li></ul><ul><li>Possible Blood types: </li></ul><ul><li>Type A – Codominant with type B. </li></ul><ul><li>Type B - Codomiant with Type A giving </li></ul><ul><li>Type AB </li></ul><ul><li>Type O – Completely Recessive </li></ul>
  15. 15. Phenotypes Genotypes <ul><li>Type A Blood AA or AO </li></ul><ul><li>Type B Blood BB or BO </li></ul><ul><li>Type AB Blood AB </li></ul><ul><li>Type O Blood OO </li></ul><ul><li>RH Factor can be Positive or Negative but is a case of complete dominance. </li></ul>
  16. 16. You be the detective! <ul><li>Is it possible for a couple, both with type A blood, to have a child with type O blood? </li></ul><ul><li>Create a Punnett Square to support your answer. </li></ul><ul><li>Is it possible for a couple, father type AB blood and mother type O blood, to have a child with type AB blood? Support your answer. </li></ul>
  17. 17. Sex-Linked Inheritance <ul><li>Some genes that have nothing to do with sex determination are on the X and Y chromosomes. </li></ul><ul><li>The genes (alleles) are described as “sex linked”. </li></ul><ul><li>Notation uses the X and Y to represent the chromosomes along with an additional letter to represent the allele on each chromosome. </li></ul>
  18. 18. Examples of Sex-linked Inheritance. <ul><li>Color blindness – genes on the X chromosome. (can’t see red and green) </li></ul><ul><li>Hemophilia – genes on the X chromosome. (blood clotting disorder) </li></ul><ul><li>Muscular Dystrophy – genes on the X chromosome. (muscles degenerate) </li></ul><ul><li>Would disorders be more common in girls or boys? Why? </li></ul>
  19. 22. Practice: <ul><li>Create a Punnett Square to show the cross between a mother who is a carrier for color blindness and a father who is color blind. </li></ul><ul><li>What are the genotypic and phenotypic results? </li></ul>