Codominance Flashcards

All 6 cards in this deck

What does codominant mean?

Both alleles are expressed in the phenotype of a heterozygous individual; neither is recessive.

What is meant by multiple alleles?

A gene that has more than two different alleles in the population, e.g. the three ABO blood group alleles.

Which alleles control the ABO blood groups, and how do they relate to each other?

Three alleles: $I^A$ and $I^B$, which are codominant with each other, and $I^O$, which is recessive to both.

Which genotypes give blood group A?

$I^AI^A$ or $I^AI^O$.

Which genotype gives blood group O?

$I^OI^O$ — two copies of the recessive allele.

True or false? In a person with blood group AB, one allele is dominant over the other.

False. $I^A$ and $I^B$ are codominant, so both are expressed and the person has both antigens.