Set Cornell Notes on pg. 6.5 up Traits and Probability 85 Patterns 2.17.2 Atoms, Ions, of Inheritance and Molecules •Topic: 7.2 Patterns of Inheritance 1. Why might polygenic traits vary more in •Essential Questions: 1. Why might polygenic traits vary more in phenotype than do single-gene traits? 2. How is codominance the same as having no dominant and recessive relationship at all between 2 alleles? phenotype than do single-gene traits? 2. 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. 6.5 Traits and Probability 84 Incomplete Dominance Codominance 7.2 Complex Patterns of Inheritance KEY CONCEPT Phenotype is affected by many different factors. 7.2 Complex Patterns of Inheritance + • What are our possible outcomes for this combination of flower color? • What if red nor white was dominant or recessive to one another? 7.2 Complex Patterns of Inheritance • 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 7.2 Complex Patterns of Inheritance – Heterozygous phenotype is intermediate between the two homozygous phenotypes – Homozygous parental phenotypes not seen in F1 offspring Green betta fish (GG) Steel blue betta fish (BB) Royal blue betta fish (GB) 7.2 Complex Patterns of Inheritance B B BR BR BR BR R R Genotype: BR Phenotype: 100% pink flowers 7.2 Complex Patterns of Inheritance B B R R BB BR Red rose Pink rose BR RR Pink rose White rose Genotype: BB, RR, BR Phenotype: 25%= red flowers 50%= pink flowers 25%= white flowers 7.2 Complex Patterns of Inheritance • Codominant alleles will both be completely expressed. – Codominant alleles are neither dominant nor recessive. Ex: multi-colored red and white rose Ex: In humans, ABO blood type. (A, B, AB, O) 7.2 Complex Patterns of Inheritance B B BR BR BR BR R R Genotype: BR Phenotype: 100% red and white flowers 7.2 Complex Patterns of Inheritance B R BB BR BR RR B R Genotype: BB, BR, RR Phenotype: 25% red flowers, 50% red-white flowers, 25% white flowers 7.2 Complex Patterns of Inheritance 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. • Polygenic traits are produced by two 7.2 Complex Patterns of Inheritance or more genes. – Can produce a continuous range of colors Ex: Skin color- 4-6 genes Eye color- at least 3 genes 7.2 Complex Patterns of Inheritance Sponge Bob Incomplete Dominance Worksheet