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Understanding Inheritance Patterns: Incomplete Dominance and Codominance

Explore how incomplete dominance and codominance influence phenotype variation in genetic traits. Learn about the blending of alleles, parent-offspring relationships, and polygenic traits like skin and eye color.

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Understanding Inheritance Patterns: Incomplete Dominance and Codominance

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  1. 7.2 Patterns of Inheritance 2.1 Atoms, Ions, and Molecules Set up Cornell Notes on pg. 85 • Topic: 7.2 Patterns of Inheritance • Essential Questions: • Why might polygenic traits vary more in phenotype than do single-gene traits? • How is codominance the same as having no dominant and recessive relationship at all between 2 alleles? • Why might polygenic traits vary more in phenotype than do single-gene traits? • How is codominance the same as having no dominant and recessive relationship at all between 2 alleles? KEY CONCEPT Phenotype is affected by many different factors.

  2. Incomplete Dominance 84 Codominance

  3. KEY CONCEPT Phenotype is affected by many different factors.

  4. + • What are our possible outcomes for this combination of flower color? • What if red nor white was dominant or recessive to one another?

  5. In incomplete dominance, neither allele is completely dominant nor completely recessive. • They are a BLEND of each other • Ex: red+white rose= pink rose BB RR BR

  6. Heterozygous phenotype is intermediate between the two homozygous phenotypes • Homozygous parental phenotypes not seen in F1 offspring Steel blue betta fish (BB) Royal blue betta fish (GB) Green betta fish (GG)

  7. B B BR BR R BR BR R Genotype: Phenotype: BR 100% pink flowers

  8. B R BB Red rose BR Pink rose B BR Pink rose R RR White rose Genotype: BB, RR, BR Phenotype: 25%= red flowers 50%= pink flowers 25%= white flowers

  9. Codominant alleles are neither dominant nor recessive. • Codominant alleles will both be completely expressed. Ex: multi-colored red and white rose Ex: In humans, ABO blood type. (A, B, AB, O)

  10. B B BR BR R BR BR R Genotype: Phenotype: BR 100% red and white flowers

  11. B R BB BR B RR BR R Genotype: Phenotype: BB, BR, RR 25% red flowers, 50% red-white flowers, 25% white flowers

  12. How to tell if we are asking you about incomplete dominance OR codominance.. The trick is to recognize when you are dealing with a question involving incomplete dominance.  There are two steps to this:  • 1) Notice that the offspring is showing a 3rd phenotype.  The parents each have one, and the offspring are different from the parents.  • 2) Notice that the trait in the offspring is a blend (mixing) of the parental traits.

  13. Polygenic traits are produced by two or more genes. • Can produce a continuous range of colors Ex: Skin color- 4-6 genes Eye color- at least 3 genes

  14. Sponge Bob Incomplete Dominance Worksheet

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