Blood Type A

While going through my paternal grandfather's wallet, I came across his Blood Bank of Delaware card.  On the back is a sticker where his blood type is written.  His blood type was A.  I never imagined I would know, or want to know, what my grandfather's blood type was, but it got me thinking.

I know that I have the same blood type as my dad, O positive, and that is different from my grandfather's.  How did my dad get his blood type?  This question lead me to do a little research since I have forgotten what I learned in school about blood types.  There is only one possible way my dad got his O blood type - both of his parents had to have passed him a gene for the type O blood.  My grandparents, however, could have had type O blood, type A blood, or type B blood.  It's all genetics.

In this day and age where DNA tests are so prevalent and helpful in doing genealogy research, it has been a breath of fresh air to find such a simple answer.