Dear Writers and Script Editors of Terminator: The Sarah Connor Chronicles

Allow me to introduce to you the basic concept of Science, and the minor matter of facts that I was taught in school at the age of 15. If Sarah Connor is blood group O negative, then her son cannot possibly be blood group AB. Using this combination as a plot point is therefore something of an error.

If I came across this kind of mistake that can be disproved by spending five minutes with google in a fanfic, it would bug me. Finding it in a professional TV series goes beyond words.