Download Bell work Blood Types - Deltona-HSA

Bell work Blood Types
1. Suppose a child is of blood type A and the
mother is of type 0. What type or types may
the father belong to?
2. 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?
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).
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).