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Incomplete & Codominance Genetics Biology 30 Mrs. S. Pipke-Painchaud Reviewing Incomplete Dominance (a.k.a. partial dominance or blending) occurs when both alleles ... – PowerPoint PPT presentation

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Title: Incomplete


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

2
Reviewing
All photos from http//www.naturalselectionrepti
les.com/Genetics.html
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 OClocks 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

http//www.usask.ca/biology/genetics/extensions/sn
apdragon.jpg
W W
w Ww Ww
w Ww Ww
5
F1 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
7
How 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

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.com/s
itebuilder/images/DSC_0040-803x536.jpg
Red Roan Example http//www.naturalselectionrepti
les.com/Genetics/exCodominance.jpg
10
Coat 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
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 LM
LM LMLM LMLM
LN LMLN LMLN
13
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