One thing I have always loved is making presentations that explain concepts through the lens of hard science. Here is something I pulled from my old records... do you know your bloodtype? And if you do, do you know what your bloodtype means?
Whatever you know, if you want further explanation, read on! And see if you can "complete the picture" on the second row of my cartoon.
Blood cells...
All the blood cells in your body are the same. Why? Because they are made in the bone marrow from stem cells carrying your DNA, which is of course, consistent in all of your cells.
Red blood cells have structures on their surface ("antigens") that we relate to the A, B or O designation. In actual fact, there are two varieties: an A antigen and a B antigen. When a person has red blood cells with A antigen, they are blood type A, when a person has red blood cells with B antigen, they are blood type B, and of course, if they have both A and B antigen they are... you get the idea, right? What if you have red blood cells with neither the A or B antigen? ...you're blood type O!
Another type of structure on the surface of some people's red blood cells is the Rhesus factor (Rh). The Rh factor relates to the positive or negative designation of your blood type. If you have the Rhesus factor, you have "+" red blood cells, if you lack the Rhesus factor, you have "-" red blood cells.