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Incomplete Dominance

Incomplete Dominance. Incomplete Dominance: The heterozygous genotype produces a phenoytype that falls in between the dominant trait and the recessive trait. Codominant vs Incomplete Dominant- What’s the difference?. Example:

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Incomplete Dominance

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  1. Incomplete Dominance Incomplete Dominance: The heterozygous genotype produces a phenoytype that falls in between the dominant trait and the recessive trait.

  2. Codominant vs Incomplete Dominant- What’s the difference?

  3. Example: In flowers, petal color demonstrates incomplete dominance. Red results when a flower has homozygous dominant alleles for the trait. White results when a flower has homozygous recessive alleles for the trait. A flower that is heterozygous for this trait will be pink. Predict the genotypic and phenotypic ratios of the offspring for the following: 1. Red and white RR x rr Genotypic Ratio: 100% Rr Phenotypic Ratio: 100% pink flowers R R r r

  4. Red= RR • White= WW • RW= pink- each allele is equally expressed to result in a blended product

  5. Example: In flowers, petal color demonstrates incomplete dominance. Red results when a flower has homozygous dominant alleles for the trait. White results when a flower has homozygous recessive alleles for the trait. A flower that is heterozygous for this trait will be pink. Predict the genotypic and phenotypic ratios of the offspring for the following: 2. Red and pink RR x Rr Genotypic Ratio: 50% RR 50% Rr Phenotypic Ratio: 50% Red flowers, 50% Pink flowers R R R r

  6. White and Pink rr x Rr Genotypic Ratio: 50% Rr 50% rr Phenotypic Ratio: 50% Pink flowers 50% White flowers r r R r Pink and Pink Rr x Rr Genotypic Ratio: 25% RR 50% Rr 25% rr Phenotypic Ratio: 25% Red flowers 50% Pink flowers 25% White flowers R r R r

  7. Codominance Codominance: condition in which both alleles of a gene are expressed in heterozygous offspring.

  8. Example 1: In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted. • Black cow and White cow BB x WW B B Genotypic Ratio: 100% BW Phenotypic Ratio: 100% Spotted cow W W

  9. Codominance • Both alleles are expressed in the phenotype • Ex. Cow Hair Color • RR – Red • WW – White • RW – Roan (Red & White)

  10. Example 1: In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted. 2. Black cow and Spotted cow BB x BW B B Genotypic Ratio: 50% BB 50% BW Phenotypic Ratio: 50% Black cow 50% Spotted cow B W

  11. Example 1: In cows black coat color and white coat color are codominant. Heterozygous offspring will be spotted. 3. Both Spotted cows BW x BW Genotypic Ratio: 25 % BB 50% BW 25% WW Phenotypic Ratio: 25% Black cow 50% Spotted cow 25% White cow B W B W

  12. Example 2: In blood typing, the gene for type A and the gene for type B are codominant. The gene for type O is recessive.

  13. Determine the possible blood types of the offspring when: 1. Mother is type O, Father is type A (homozygous) O O Genotypic Ratio: 100% AO Phenotypic Ratio: 100% Type A Blood A A

  14. Determine the possible blood types of the offspring when: 2. Mother is type AB, Father is Type A (heterozygous) Genotypic Ratio: 25 % AA 25% AO 25% AB 25% BO Phenotypic Ratio: 50% Type A Blood 25% Type AB Blood 25% Type B Blood A B A O

  15. Determine the possible blood types of the offspring when: 3. Mother is type A (heterozygous), Father is type B (heterozygous) Genotypic Ratio: 25 % OO 25% AO 25% AB 25% BO Phenotypic Ratio: 25% Type O Blood 25% Type A Blood 25% Type AB Blood 25% Type B Blood A O B O

  16. Determine the possible blood types of the offspring when: 4. Mother is type B (homozygous), Father is type A (homozygous) B B Genotypic Ratio: 100% AB Phenotypic Ratio: 100% Type AB Blood A A

  17. More on blood types….. • The blood type determines what antibodies are located within the blood. Type A blood has type B antibodies. If type B blood is put into their bodies, their immune system reacts as if it were a foreign invader, the antibodies clump the blood - can cause death. • Type AB blood has no antibodies, any blood can be donated to them - they are called the "universal acceptors" • Type O blood has no surface markers on it, antibodies in the blood do not react to type O blood, they are called the "universal donors"

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