Blood Typing and Genetic Inheritance: A Biology Explanation

Question
I am a college student taking a general biology lab course.  One of our questions involves two families who think that their babies may have been switched at birth.  They have blood typing tests done to see if in fact the children have been switched.  We do not know what blood types when blended create other blood types... can you help?

Thanks so much!

Answer
You've got to look at how the genetics of blood typing affect the phenotype.  Try searching Google for "genetics of blood type".

These are two reasonable sites I came across that may help.

http://www.biology.arizona.edu/human_bio/problem_sets/blood_types/Intro.html

http://www.paternityangel.com/Articles_zone/Blood/BloodType1.htm