Blood types have 3 alleles. I^A and I^B are both dominant to I^o. I^A and I^B are co-dominant with each other.

There are four babies in a maternity ward. Their blood groups are:

* Baby 1: Type A

* Baby 2: Type B

* Baby 3: Type AB

* Baby 4: Type O

There are four sets of parents, with blood groups as follows:

* Smiths: AB x O

* Browns: A x O

* Joneses: A x AB

* Wilsons: O x O

Which baby belongs to which family?

(Hint: start by assigning genotypes to each blood type. Then start with the babies you can assign for sure and get the rest by process of elimination).

Baby 1: Browns

Baby2: Smiths

Baby3: Joneses

Baby4: Wilsons

The Wilsons both have type O bloodm (I^oI^o), so their baby must be type O (baby 4).

The genotypes of the Browns are less certain: one must be I^oI^o but the other could be either I^AI^o or I^AI^A. That means the baby could be either AO or OO. Since we know baby 4 belongs to the Wilsons, baby 1 must belong to the Browns.

The only way to have type AB blood is for one parent to have at least one A and the other to have at least one B. That means baby 3 must be the Jones'.

So, baby 2 must blong to the Smiths.