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Incomplete & Codominance

Incomplete & Codominance. Genetics Biology 30 Mrs. S. Pipke-Painchaud. Reviewing. All photos from: http://www.naturalselectionreptiles.com/Genetics.html. Incomplete Dominance. (a.k.a. partial dominance or blending) 

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Incomplete & Codominance

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

  2. Reviewing All photos from: http://www.naturalselectionreptiles.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 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 http://www.usask.ca/biology/genetics/extensions/snapdragon.jpg

  5. http://www.visionlearning.com/library/modules/mid129/Image/VLObject-3228-050216120240.jpghttp://www.visionlearning.com/library/modules/mid129/Image/VLObject-3228-050216120240.jpg 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 ***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/tutorials/tutorial5_files/figure_14_9.gifhttp://courses.bio.psu.edu/fall2005/biol110/tutorials/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 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.com/sitebuilder/images/DSC_0040-803x536.jpg Red Roan Example: http://www.naturalselectionreptiles.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

  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

  13. Resource Sites

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