Non-Mendelian Genetics Exceptions to Mendel’s Dominance and Recessives

Incomplete Dominance Snapdragon Flowers

Red Snapdragon x White Snapdragon What do you think will happen? Cross- pollinate- If we followed Mendel’s Law one would be dominate over the other

Incomplete Dominance If you cross a red snapdragon (RR) with a white snapdragon (WW)  RW R WW Givens: Red = RR White = WW Pink = RW You get all PINK flowers (RW)

Incomplete Dominance Blending in the phenotypes of offspring (where did we see blending?) Cross two different phenotypes and you get a third phenotype RR x WW = RW all pink ( 2 different letters and both capitals) Phenotype Genotype

Incomplete Dominance When F1 generation (all pink flowers) is self –pollinated? Cross_____ x ______ Genotype Phenotype

Incomplete dominance R R W WW R W RW RW ___ Red ___ Pink ___ White

What happens if you cross a pink with a white? A pink with a red? Incomplete dominance  

Incomplete Dominance Other Examples: Hair Texture: Curly hair is incompletely dominant (HH) to straight hair (SS). Those who have wavy hair are intermediate (HS).

Codominance - both genes contribute to the phenotype (not blending, both are present) - Think “Co-captain” – both are equals, together

Codominance Both genes are Dominant -Certain types of Chickens have black feathers or white feathers. -Heterozygous chickens, will have both black and white feathers ( black and white do not blend but appear separately)

Codominance Examples Codominance is seen in animals such as cattle Red=RR, White=WW Roan=RW  red and white together Cross_____ x ______