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 DominanceIf you cross a red snapdragon (RR) with a
white snapdragon (WW)
RW
R R WWGivens: 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 R W
R W
WW
R W R
W
___ 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=WWRoan=RW red and white together
Cross_____ x ______
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