6C. Patterns of Inheritance (Part 2 – Codominant & Incomplete Traits) Chapter 7.1 & 7.2

Incomplete Dominance In incomplete dominance, neither allele is completely dominant nor completely recessive. B = Blue and b = Green BB = Blue bb = green Bb = Teal When both alleles are present (heterozygous) the traits blend Sometimes, you may use two different letters Example: B = Blue G= Green

Codominance In codominance, both alleles are dominant. B = Yellow and b = Black BB = Yellow bb = black Bb = Yellow & Black When both alleles are present (heterozygous) then both traits show Sometimes, you may use two different letters Example: Y = Yellow B= Black

Review & Compare Red Pig Red & Blue Pig Purple Pig In Flying Pigs A = Red a = Blue If the trait was normal inheritance, what would the phenotype be for a “Aa”? Red Pig If the trait was Codominant, what would the phenotype be for a “Aa”? Red & Blue Pig If the trait was Incomplete Dominance, what would the phenotype be for a “Aa”? Purple Pig

Many genes may interact to produce one trait. Polygenic traits are produced by two or more genes. Example – AaBbCCDd code for one phenotype Order of dominance: brown > green > blue.

AaBb aaBb Aabb aabb Black Yellow Chocolate Yellow An epistatic gene can interfere with other genes. For example – in Labs you can have either a Black, yellow or chocolate lab B = Black b= Chocolate BUT a = yellow and it is epistatic, which means if the dog inherits a “a” the dog is yellow, it doesn’t matter what if they are BB, Bb, bb What color is the dog? AaBb Black aaBb Yellow Aabb Chocolate aabb Yellow

The environment interacts with genotype. Phenotype is a combination of genotype and environment. The sex of sea turtles depends on both genes and the environment Height is an example of a phenotype strongly affected by the environment.