7.1.3 Codominance and Multiple Alleles

• In incomplete dominance, the phenotype is a blend of the two alleles
• In complete dominance, the dominant allele completely masks the expression of the recessive allele.
• Match the example of codominance with its explanation:

  ABO blood group system ↔️ The A and B alleles are codominant, resulting in the AB blood type

  Roan coat color in cattle ↔️ Codominance between red and white alleles results in a blend of red and white hairs
• What are examples of multiple alleles?

  ABO blood groups
• What happens in the inheritance pattern called dominance?

  One allele masks the others
• What blood type do individuals with the OO genotype have?

  O
• What blood type results from the codominance of the A and B alleles?

  AB
• In complete dominance, the dominant allele completely masks the expression of the recessive allele.
• Order the inheritance patterns from least to most alleles involved:

  1️⃣ Dominance

  2️⃣ Codominance

  3️⃣ Multiple Alleles
• What is codominance?

  Both alleles are expressed
• What happens to both alleles in codominance?

  Both are fully expressed
• What is the phenotype of a heterozygote in codominance?

  Both alleles are evident
• What are multiple alleles?

  More than two alleles
• When a gene has multiple alleles, the inheritance patterns can involve dominance, codominance, or additive effects.


  True
• In codominance, both alleles are fully expressed in the phenotype
• Multiple alleles refer to the existence of more than two alleles for a single gene in a population.
• Codominance occurs when two different alleles are both fully expressed in the phenotype of the heterozygous individual.
• Match the example with its explanation:

  ABO blood group system ↔️ A and B alleles are codominant

  Roan coat color in cattle ↔️ Red and white alleles are codominant
• Which alleles in the ABO blood group system are codominant?

  A and B
• In complete dominance, one allele is fully expressed, while the other is not expressed.


  True
• In codominance, both alleles are expressed equally in the phenotype.


  True
• What happens to the recessive allele in complete dominance?

  It is masked
• Genes with multiple alleles have more than two possible forms of the allele.
• Describe the inheritance patterns of the ABO blood group system:

  1️⃣ A and B alleles are codominant, resulting in the AB blood type

  2️⃣ The O allele is recessive, so individuals with the OO genotype have the O blood type

  3️⃣ The A and B alleles are dominant over the O allele
• In the ABO blood group system, the A and B alleles are codominant.

  True
• In dominance, one allele masks the expression of the other.


  True
• In codominance, both alleles are evident in the phenotype of heterozygotes.


  True
• In additive effects, alleles contribute quantitatively to the trait.