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Dominance and Multiple Alleles

Dominance and Multiple Alleles. Genetic Interactions. Incomplete dominance – When the alleles are blended and the offspring have a mix of their parent traits. ex. Snap Dragons R = red r = white Offspring can be pink !. white. Genetic Interactions.

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Dominance and Multiple Alleles

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  1. Dominance and Multiple Alleles

  2. Genetic Interactions Incomplete dominance – When the alleles are blended and the offspring have a mix of their parent traits. ex. Snap Dragons R = red r =white Offspring can be pink! white

  3. Genetic Interactions Codominance – in this case both alleles are expressed. BB= black corn YY= yellow corn BY = black and yellow corn Heterozygous genotype

  4. Incomplete Dominance or Codominance?

  5. Incomplete Dominance or Codominance?

  6. Incomplete or Codominance?

  7. Polygenic Traits • A polygenic trait is determined by multiple genes. (poly=many, genic=genes) Example: eye color and height

  8. Multiple Alleles Remember: - Chromosomes occur in pairs. (homologous pairs) - The different alleles of a gene occupy the same positions on each chromosome

  9. Multiple Alleles So far each gene we have discussed has been made of two possible alleles. Ex. B = blue b= yellow R = red r = white

  10. Multiple Alleles However, it is possible to have several different allele possibilities for one gene. Multiple alleles is when there are more than two allele possibilities for a gene.

  11. Multiple Alleles In traits with multiple alleles, each individual can carry any two of the several possible alleles. Ex. BLOOD TYPE The gene for blood type has 3 possible alleles. IA, IB, and i

  12. Blood Type In this case both A and B are dominant to O (recessive). A and B are codominant (both expressed) So... there are four human blood types

  13. Blood Type

  14. Blood Type Practice Problems: 1. A mother is AB and a father is O. Draw the punnett square. IA IB i i What is the probability their offspring will have A type blood? ____ Can they have an offspring with O blood? ____

  15. Blood Type 2. A mother is IAi and a father is IB IB. Draw the punnett square. What is the probability their offspring will have B type blood? Can they have an offspring with O blood?

  16. Blood Type 3. If a child has AB blood which of the following could NOT be the parents? a) ii, IAIB b) IAi, IBIB c) IBIB, IAIA d) IAi, IBi

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