Essentially I'm wondering if this is splittable from Hollywood Genetics
. I noticed on AB Negative
that there were plenty of examples dealing with wrong blood types except that trope is actually about people always having ultra rare or special blood types when they are mentioned (even though the one they mention, usually AB Negative, isn't really rare).
Since blood type is different from hair colour and facial features due to the fact that it doesn't depend on casting, I figure it should be split off.
Examples ripped from AB Negative
- * on Law and Order SVU, when a comatose woman's mysterious pregnancy is under investigation. Her blood type is A and the fetus's is AB, so the investigators conclude that its father must be type B ... even though a type AB father would also have a 50/50 chance of passing the B trait on to his child. Particularly deserving of a You Fail Genetics Forever is Wong, who agrees that the father's type must be B despite his own medical training.
- And again on SVU, they assert that two type A parents must have a type A child (the child could also be type O). And then, after learning the supposed daughter is type B, they assert that the mother could not possibly be her mother. (The daughter could have one (heterogenous) type A parent, so she might just have a different father.)
- In Terminator: The Sarah Connor Chronicles, they mentioned that Sarah had O- blood but John had AB- blood; this would mean that she couldn't possibly be his mother, barring vanishingly rare situations like mutation or Bombay blood type[[hottip:*:For the record, type O is recessive, and Sarah is therefore by necessity homozygous for O. Johny could be AO (type A) or BO (type B), but type AB is not possible]]. Note that Sarah being unable to give blood to the AB- Derek Reese despite being a universal donor could be correct, since she's giving whole blood containing plasma, not just blood cells, and compatibility for plasma is reversed compared to blood cells -- someone with type O is the least useful donor because their plasma could contain antibodies against non-O blood types.
- This is confirmed (again) from Robert A. Heinlein's I Will Fear No Evil where Johann explains how he loved his son more than life itself, even though he knew that his son's blood type was O and his was AB, he has to explain he knew from birth that his son wasn't his because the blood typing was incompatible.