1. Incomplete & Codominance
Genetics
Biology 30
Mrs. S. Pipke-Painchaud

2. Reviewing
All photos from:

3. Incomplete Dominance (a.k.a. partial dominance or blending)
occurs when both alleles contribute to a trait that is not like either parent. 
this condition is only seen in the heterozygous individual 
ex.. Snap Dragons or Four O’Clocks or Morning Glory or Primrose (Flowers)
Curly (homozygous) or straight (homozygous), but if you are heterozygous you have wavy hair.

4. Example: Snap Dragons Parents: Red X White W = red w = white
 Parents are both true breeding red and white.
WW  X ww 
Genotype: All Ww
Phenotype: All Pink W w Ww

5. F1 x F1 Cross Ww X Ww Genotypic Ratio: 1WW: 2 Ww: 1ww
F1 x F1 Cross
Ww X Ww
Remember:
W = red  w =  white Ww = pink
Genotypic Ratio:
1WW: 2 Ww: 1ww
Phenotypic ratio:
1 Red: 2 Pink: 1 White W w WW Ww ww
***NOTE:  Because there is no dominance in the heterozygote the phenotypic ratio is identical to the genotypic ratio**** 

6. http://courses. bio. psu

7. How the coloring works . . . WW – have enough pigment to be red
ww  -  flowers don’t have any pigment = no color
Ww – only have enough pigment to be pink

8. Codominance the two dominant genes are expressed at the same time
both traits appear in the heterozygous individual at the same time
ex.. Roan (Red or Blue) coat color in horses and cattle 
Chestnut and White color in horses are both dominant traits; the heterozygous individual is a palomino (golden).

9. Blue Roan Example: http://www. virginiacowboy
Red Roan Example:

10. Coat Color in Horses CR CW CR CW C= Color gene
CR CR  = Red CW CW = White
CR CW = Red Roan
If you cross a true breeding Red horse with a true breeding white horse, what ratios will you get?
Genotypic Ratio:
All CR CW
Phenotypic Ratio:
All Red Roan CR CW
CR CW

11. Example: MN Blood Group
MN blood group – is characterized by a certain type of glycoprotein on the surface of the RBCs. 
There are two forms: M and N
Designate is L
LMLM = M
LNLN = N
LMLN  = MN type 

12. MN Blood Group
LMLM = M
LNLN = N
LMLN  = MN type 
What types of offspring would be produced from a cross of a homozygous M type with an MN type?
Parents: LMLM X LMLN
Genotypic Ratio:
1 LMLM : 1 LMLN
Phenotypic Ratio:
1 M blood type: 1 MN blood type LM
LMLM LN
LMLN

13. Resource Sites