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Incomplete Dominance

Learn about incomplete dominance, where heterozygous genotypes show an intermediate phenotype, and codominance, expressing both alleles. Explore examples in flowers and cows, predict offspring ratios, and understand blood type inheritance scenarios. Enhance your genetic knowledge!

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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. 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

  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: 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

  4. 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

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

  6. 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

  7. 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

  8. 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

  9. 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.

  10. 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

  11. 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

  12. 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

  13. 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

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