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 ______