Title: Incomplete
1Incomplete Codominance
- Genetics
- Biology 30
- Mrs. S. Pipke-Painchaud
2Reviewing
All photos from http//www.naturalselectionrepti
les.com/Genetics.html
3Incomplete 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 OClocks or Morning
Glory or Primrose (Flowers) - Curly (homozygous) or straight (homozygous), but
if you are heterozygous you have wavy hair.
4Example 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
http//www.usask.ca/biology/genetics/extensions/sn
apdragon.jpg
W W
w Ww Ww
w Ww Ww
5F1 x F1 Cross
http//www.visionlearning.com/library/modules/mid1
29/Image/VLObject-3228-050216120240.jpg
- 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
W WW Ww
w 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.edu/fall2005/biol110/tutori
als/tutorial5_files/figure_14_9.gif
http//library.thinkquest.org/20465/media/flowers.
gif
7How the coloring works . . .
- WW have enough pigment to be red
- ww - flowers dont have any pigment no
color - Ww only have enough pigment to be pink
8Codominance
- 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).
9Blue Roan Example http//www.virginiacowboy.com/s
itebuilder/images/DSC_0040-803x536.jpg
Red Roan Example http//www.naturalselectionrepti
les.com/Genetics/exCodominance.jpg
10Coat Color in Horses
- 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 CR
CW CR CW CR CW
CW CR CW CR CW
11Example 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
12MN 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 LM
LM LMLM LMLM
LN LMLN LMLN
13Resource Sites