Reviewing All photos from: http://www.naturalselectionreptiles.com/Genetics.htmlhttp://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. 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.
Example: Snap Dragons C R = red C W = white Parents are both true breeding red and white. Parents: Red X White C R C R X C W C W Genotype: All C R C W Phenotype: All Pink CRCR CRCR CWCW CRCWCRCW CRCWCRCW CWCW CRCWCRCW CRCWCRCW http://www.usask.ca/biology/genetics/extensions/ snapdragon.jpg
F1 x F1 Cross C R C W X C R C W Remember: C R = red C W = white Genotypic Ratio: 1 C R C R : 2 C R C W : 1 C W C W Phenotypic ratio: 1 Red: 2 Pink: 1 White CRCR CWCW CRCR CRCRCRCR CRCWCRCW CWCW CRCWCRCW CWCWCWCW ***NOTE: Because there is no dominance in the heterozygote the phenotypic ratio is identical to the genotypic ratio**** http://www.visionle arning.com/library/ modules/mid129/Im age/VLObject- 3228- 050216120240.jpg
How the coloring works... C R C R = have enough pigment to be red. C W C W = flowers don’t have any pigment. = no color C R C W = only have enough pigment to be pink.
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).
Red Roan Example: http://www.naturalselecti onreptiles.com/Genetics/ exCodominance.jpg http://www.naturalselecti onreptiles.com/Genetics/ exCodominance.jpg
Blue Roan Example: http://www.virginiacowboy.com/sitebuilder/images/DSC_0040 -803x536.jpg http://www.virginiacowboy.com/sitebuilder/images/DSC_0040 -803x536.jpg Red Roan Example: http://www.brokenlfarm.com/images/sale/kbrowdypetejr/102_84 24.JPG
Coat Color in Horses C= Color gene C R C R = Red C W C W = White C R C W = Red Roan If you cross a true breeding Red horse with a true breeding white horse, what ratios will you get? Genotypic Ratio: All C R C W Phenotypic Ratio: All Red Roan CRCR CRCR CWCW C R C W CWCW
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 L M L M = M L N L N = N L M L N = MN type
MN Blood Group L M L M = M L N L N = N L M L N = MN type What types of offspring would be produced from a cross of a homozygous M type with an MN type? Parents: L M L M X L M L N Genotypic Ratio: 1 L M L M : 1 L M L N Phenotypic Ratio: 1 M blood type: 1 MN blood type LMLM LMLM LMLM LMLMLMLM LMLMLMLM LNLN LMLNLMLN LMLNLMLN
Multiple Alleles More than two alleles for a gene
O (ii) is recessive to I A and I B. Genotypes I A I A and I A i result in Type A phenotype. Genotypes I B I B and I B i result in Type B phenotype. Genotype I A I B results in Type AB phenotype (codominant). Genotype ii results in Type O phenotype.
Surface proteins are like nametags and antibodies clump up foreign blood Useful in blood transfusion and organ transplant
Resource Sites Incomplete & Codominance Explained: –http://www.hobart.k12.in.us/jkousen/Biology/inccodom.htmhttp://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/http://www.brightstorm.com/science/biology/mendelian- genetics/codominance-incomplete-dominance/ Practice: Drag and Drop Pedigrees –http://www.zerobio.com/drag_gr11/pedigree/pedigree4.htmhttp://www.zerobio.com/drag_gr11/pedigree/pedigree4.htm More Practice from KSU: –http://www.ksu.edu/biology/pob/genetics/incom.htmhttp://www.ksu.edu/biology/pob/genetics/incom.htm