1. Bell work Blood Types
Suppose a child is of blood type A and the mother is of type 0. What type or types may the father belong to?
Suppose a father and mother claim they have been given the wrong baby at the hospital. Both parents are blood type A. The baby they have been given is blood type O. What evidence bearing on this case does this fact have?

2. Answers
1. Since the mother can only provide alleles for O type blood (i), the father must provide the allele for blood type A (IA). Three genotypes can provide the IA allele: IA IA (blood type A), IA i (blood type A), or IA IB (blood type AB). So the father must be either blood type A or blood type AB. The child (with blood type A) must be heterozygous, IA i (remember the O allele, i, is recessive to both the A and the B alleles).

3. Answers
2. It is possible that both parents are heterozygous (IA i ). In which case, it would be possible to produce a type O child 25% of the time (see Punnett square diagram below).