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Incomplete & Codominance

Incomplete & Codominance. Reviewing. All photos from: http://www.naturalselectionreptiles.com/Genetics.html. Incomplete Dominance. (a.k.a. partial dominance or blending)  occurs when both alleles contribute to a trait that is not like either parent. 

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Incomplete & Codominance

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  1. Incomplete & Codominance

  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 CR= red  CW=  white   Parents are both true breeding red and white. Parents: Red  X  White CRCRX CWCW Genotype: All CRCW 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 CRCWX CRCW Remember: CR = red  CW =  white  Genotypic Ratio: 1CRCR: 2 CRCW: 1 CWCW 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 . . . • CRCR = have enough pigment to be red. • CWCW =flowers don’t have any pigment. = no color • CRCW = 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. Red Roan Example: http://www.naturalselectionreptiles.com/Genetics/exCodominance.jpg

  10. Red Roan Example: http://www.brokenlfarm.com/images/sale/kbrowdypetejr/102_8424.JPG Blue Roan Example: http://www.virginiacowboy.com/sitebuilder/images/DSC_0040-803x536.jpg

  11. Coat Color in Horses • C= Color gene • CRCR  = Red • CWCW= White • CRCW= Red Roan • If you cross a true breeding Red horse with a true breeding white horse, what ratios will you get? Genotypic Ratio: All CRCW Phenotypic Ratio: All Red Roan

  12. 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

  13. 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

  14. Multiple Alleles • More than two alleles for a gene

  15. O (ii) is recessive to IA and IB. • Genotypes IAIAand IAi result in Type A phenotype. • Genotypes IBIB and IBi result in Type B phenotype. • Genotype IAIBresults in Type AB phenotype (codominant). • Genotype ii results in Type O phenotype.

  16. Surface proteins are like nametags and antibodies clump up foreign blood • Useful in blood transfusion and organ transplant

  17. Resource Sites • Incomplete & Codominance Explained: • http://www.hobart.k12.in.us/jkousen/Biology/inccodom.htm • Codominance - Incomplete Dominance (Brightstorm Video) • http://www.brightstorm.com/science/biology/mendelian-genetics/codominance-incomplete-dominance/ • Practice: Drag and Drop Pedigrees • http://www.zerobio.com/drag_gr11/pedigree/pedigree4.htm • More Practice from KSU: • http://www.ksu.edu/biology/pob/genetics/incom.htm

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