- A curious adult from Alaska
October 15, 2015
No it doesn’t. Neither of your parents has to have the same blood type as you.
For example if one of your parents was AB+ and the other was O+, they could only have A and B kids. In other words, most likely none of their kids would share either parent’s blood type.
And that’s just one of many possibilities. There are lots of other possible combinations where two parents without blood type A can have a child with one. Here they are:
Two Copies of Each Gene, One from Each Parent
DNA is a set of instructions for making and running a living thing. So your DNA is the set of instructions for making and running you.
A lot of these instructions are found in long stretches of DNA called genes. Each gene has the instructions for one small part of you.
One of these genes goes by the name ABO. It comes in three flavors, or “alleles” —A, B, and O. Your blood type is determined by the combination of alleles of this gene you get from your parents.
Another Gene Determines Positive/Negative
So now I know what you’re thinking – you’re A positive, so what does the “positive” part mean? It turns out there’s another important molecule on blood cells called the Rh protein.
You either have the Rh protein or you don’t. If you have it, you’re positive, and if you don’t, you’re negative. If you’re interested in knowing more about the Rh protein, you can visit one of our previous Ask a Geneticist answers.