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Incomplete & Codominance. Reviewing All photos from:

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Presentation on theme: "Incomplete & Codominance. Reviewing All photos from:"— Presentation transcript:

1 Incomplete & Codominance

2 Reviewing All photos from:

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 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 snapdragon.jpg

5 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 modules/mid129/Im age/VLObject- 3228- 050216120240.jpg

6 005/biol110/tutorials/tutorial5_f iles/figure_14_9.gif 005/biol110/tutorials/tutorial5_f iles/figure_14_9.gif 5/media/flowers.gif

7 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.

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.naturalselecti exCodominance.jpg http://www.naturalselecti exCodominance.jpg

10 Blue Roan Example: -803x536.jpg -803x536.jpg Red Roan Example: 24.JPG

11 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

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 L M L M = M L N L N = N L M L N = MN type

13 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

14 Multiple Alleles More than two alleles for a gene

15 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.

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: – Codominance - Incomplete Dominance (Brightstorm Video) – genetics/codominance-incomplete-dominance/ genetics/codominance-incomplete-dominance/ Practice: Drag and Drop Pedigrees – More Practice from KSU: –

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