What is meant by the term codominance?
Reveal answer
Both alleles in a heterozygote contribute detectably to phenotype.
Key words: codominance
4(b) INHERITANCE · RECALL
4.21B Codominance
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What is meant by the term ABO blood group?
Reveal answer
Blood classification determined by A and B red-cell antigens.
Key words: ABO blood group
What is meant by the term incomplete dominance?
Reveal answer
Heterozygote has an intermediate phenotype in the stated model.
Key words: incomplete dominance
Allele interactions, Complete dominance. Heterozygote? Example model?
Reveal answer
Heterozygote: Matches dominant homozygote. Example model: Aa shows A trait.
Key words: Complete dominance
Allele interactions, Codominance. Heterozygote? Example model?
Reveal answer
Heterozygote: Both allele products detectable. Example model: IᴬIᴮ gives AB.
Key words: Codominance
Allele interactions, Incomplete dominance. Heterozygote? Example model?
Reveal answer
Heterozygote: Often intermediate phenotype. Example model: Red × white gives pink model.
Key words: Incomplete dominance
Allele interactions, Recessive expression. Heterozygote? Example model?
Reveal answer
Heterozygote: Seen without dominant allele. Example model: aa.
Key words: Recessive expression
True or false, and why? “Codominance means the alleles blend permanently.”
Reveal answer
False. Both remain distinct and can be inherited separately.
True or false, and why? “AB is a new allele.”
Reveal answer
False. It is the phenotype produced by genotype IᴬIᴮ.
True or false, and why? “Uppercase always means dominant in codominance.”
Reveal answer
False. Use defined superscripts because neither codominant allele masks the other.
Define codominance.
Reveal answer
Both alleles are expressed in the phenotype of a heterozygote.
Key words: expressed
Give a human example of codominance.
Reveal answer
ABO blood groups: Iᴬ and Iᴮ together give blood group AB.
Key words: ABO
Parents with genotypes Iᴬi and Iᴮi have children. Which blood groups are possible?
Reveal answer
A, B, AB and O, each with a probability of 1 in 4.
Key words: AB
Which ABO allele is recessive?
Reveal answer
i (the O allele), recessive to both Iᴬ and Iᴮ.
Key words: recessive
Why does a person with genotype Iᴬi have blood group A?
Reveal answer
Iᴬ is dominant to i → only the A antigen is made.
Key words: dominant