Genetic Crosses


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Genetic Crosses

  1. 1. Genetic Crosses
  2. 2. Incomplete Dominance <ul><li>One allele for a trait is not dominant over the other </li></ul><ul><li>Heterozygous condition produces a phenotype that is intermediate of the two alleles </li></ul><ul><li>Use capital form of two different letters </li></ul>
  3. 3. Incomplete Dominance Red Snaps White Snaps RR WW RW All Pink RW X RW
  4. 4. Codominance <ul><li>One allele for a trait is not dominant over the other </li></ul><ul><li>The heterozygous condition produces a phenotype in which both variations appear </li></ul>
  5. 5. Codominance
  6. 6. Try these two <ul><li>In cats when a long tailed cat is bred with a no tailed cats short tailed cats are produced. If a short tailed cat was bred with a no tailed cat, what is the likelihood that a short tailed cat would be produced? Is this incomplete or codominance? </li></ul><ul><li>2) Also in cats a black haired cat and a white haired cat produce a tuxedo (mix of black and white). If a two tuxedo cats were bred, what would be the likelihood of producing a white cat? Is this incomplete or codominance. </li></ul>
  7. 7. Sex-Linked Traits Activity Hemophiliac Male X h Y Normal Male X H Y Hemophiliac Female X h X h Carrier Female X H X h Normal Female X H X H Overall Total Group Total Phenotype Genotype
  8. 8. Sex Linked Traits <ul><li>Traits that have a gene (allele) located on a sex-chromosome. Most traits the gene is located on the X chromosome </li></ul><ul><li>Since males have only one of two X chromosomes they only need one recessive gene to carry the trait. </li></ul><ul><li>Must include sex chromosome in cross </li></ul><ul><li>Examples are colorblindness and hemophilia </li></ul>
  9. 9. Colorblindness Test
  10. 10. Sex-linked Trait example <ul><li>Normal vision is dominant to colorblindness. A heterozygous (carrier) female marries a normal male. </li></ul>
  11. 11. 3-2-1 Think about <ul><li>List 3 human traits that seem to have a range of possible variations (rather than simply 2 or even 3 distinct variations) </li></ul><ul><li>Describe 2 reasons why you think traits could have a range of variations </li></ul><ul><li>Give one definition for the word POLYGENIC </li></ul>
  12. 12. Polygenic Traits <ul><li>Traits controlled by more than one gene. </li></ul><ul><li>Usually creates a range of variations possible </li></ul><ul><li>Examples: Eye color, skin color, hair color, height </li></ul><ul><li>See Child/Grandchild lab for examples </li></ul>
  13. 13. Answer the following <ul><li>How similar or different does your child look compared to you in terms of hair, eye, or skin color? </li></ul><ul><li>How could the genotypes of the child change to make them look more/less similar than you? </li></ul>
  14. 14. Multiple Alleles <ul><li>More than two alleles (gene variations) for a trait. </li></ul><ul><li>Example A B O blood types </li></ul>
  15. 15. Blood Type Donate /Receive ii O I A I B AB I B I B I B i B I A I A I A i A Antibody for: Antigen on Blood Genotype Blood Type
  16. 16. Blood Type Examples <ul><li>A woman with O blood and man with A blood marry. Could they have a child with O blood? Could it be possible that there is no chance of having children with O blood? </li></ul><ul><li>A man with B blood marries a woman with AB blood. They have a child with A blood. What has to be dads genotype? Prove it. </li></ul><ul><li>A man with A blood (I A I A ) and woman with B blood (I B I B ) have a child. The child needs a blood transfusion. Do they need to worry about the child getting the wrong type of blood? Why or why not? </li></ul>