Answer:
Mrs. Ritter, whose blood type is B (Bi) is right in claiming that Ian - blood type A (Ai)- is the father of her baby, with blood type O (ii). Ex-boyfriend AB (AB) cannot be the father.
Step-by-step explanation:
The blood type, according to the ABO system, is determined by the presence or absence of surface antigens A and B. In addition, genotypes can be co-dominant, in the case of A, B and AB, heterozygous (Ai or Bi) and recessive, in the case of group O (ii)
- Type A contains the antigen A and its genotype can be AA or Ai.
- Type B contains the antigen B, whose genotype can be BB or Bi.
- Type AB contains both antigens and a single genotype expression AB.
- Type O blood lacks surface antigens, its genotypic expression being ii.
According to this, to check if Mrs Ritter's baby is Ian's child, a crossing can be done:
♂ Ai
♀ Bi
Alleles A i
B AB Bi
i Ai ii
Ian and Mrs Ritter have a 25% chance of having a child with blood type O (ii), so the baby may be Ian's child.
To find out why the ex-boyfriend can't be the father
♂ AB
♀ Bi
Alleles A B
B AB BB
i Ai Bi
It is not possible that Mrs. Ritter's ex-boyfriend is the father of the baby, as the possible offspring in the crossover are A, B or AB.