Professor: If both parents have type O blood then their children can only have type O blood. This is a genetic law.S...

Mehran on July 19, 2018

Hi @YHD, thanks for your post.

We can diagram the professor's statement as:
P1 (O) and P2 (O) ==> C (O)
(If both parents have type O blood, then their children can only have type O blood)

The student "objects" to the professor, saying "I have Type O blood, and my dad has Type B." The student has misinterpreted the professor's statement. He thinks that the professor has said that a parent *must* have Type O blood for a child to have Type O blood (i.e., that it is *necessary* for a parent to have Type O blood if a child is to have Type O blood). Of course, the professor did not say this. Rather, the professor said that it is *sufficient*, if both parents have Type O blood, to result in children with Type O blood.

If you were to diagram the student's misinterpretation of the professor's statement, it would look like this:
C (O) ==> P (O)

(If a child has Type O blood, then the parent must have Type O blood).

Hope this helps! Please let us know if you have any additional questions.