The children of couples in which one partner has blood type O (genotype ii) and the other partner has blood type AB (genotype IᴬIᴮ) are studied. What is the expected concordance rate for blood type of DZ twins in this study? Explain why this answer is different from the answer to part (a).

Key Concepts

Blood Type Inheritance

Blood type is determined by the ABO gene, which has three alleles: A (Iᴬ), B (Iᴮ), and O (i). Individuals with blood type O have the genotype ii, while those with blood type AB have the genotype IᴬIᴮ. The offspring of these parents can inherit one allele from each parent, leading to possible blood types A (Iᴬi) and B (Iᴮi), but not AB or O.

Dizygotic (DZ) Twins

Dizygotic twins, or fraternal twins, arise from two separate eggs fertilized by two different sperm cells. They share about 50% of their genetic material, similar to regular siblings. In the context of blood type inheritance, the genetic variation between DZ twins can lead to different blood types, depending on the alleles they inherit from their parents.

Concordance Rate

Concordance rate refers to the likelihood that both twins in a pair exhibit the same trait or characteristic, such as blood type. In this study, the expected concordance rate for DZ twins would be lower than for monozygotic twins due to their genetic differences. This rate is influenced by the genetic combinations possible from the parents' blood types, leading to varied outcomes among the twins.