![]() O: Possible if the AB parent is a chimera or has cis-AB blood type. For example, it does not include mutation and uniparental disomy, as they have the fewest documented examples of blood type rule breaking.ī: Possible if either parent is a chimeraĪB: Possible if either parent is a chimera The chart below does not cover every scenario. Īpplying the rare exceptions to different scenarios If this happened with the chromosome that contains the blood type genes, you could theoretically inherit your blood type entirely from one parent. There are documented examples where a child inherits both copies of a chromosome from a single parent 6. This is the rarest possibility mentioned so far, and may be difficult to confirm aside from ruling out the other possibilities. This blood type is most common in Taiwan (1 in 8,000 people) and India (1 in 10,000 people) 5. People with this blood type look like Type O, no matter which versions of the ABO gene they have. This rare, recessive blood type is caused by a variant at a different blood type gene. This blood type is most common in some southeast Asian populations like Korea (1 in 3,000 people) and Japan (1 in 80,000 people) 4. This can make it possible for an AB parent to have an O child, and an AB parent + O parent to have an AB child. This rare blood type is caused by a fourth version of the ABO gene, which can cause Type AB all by itself. Read more on chimerism and blood chimerism. Around 1 in 12 twin pairs and 1 in 5 triplet pairs show blood chimerism 3. This can cause a different blood type than the DNA in the sperm/egg cells. This is when fraternal twins share some blood during pregnancy, causing one or both twins to have mixed blood cells. ![]() It is theorized to be highest in IVF pregnancies. Only about 100 cases of chimerism have been reported 1, though as it often goes undetected the true frequency is unknown. If the blood type is made by one “twin” while the sperm/eggs are made by the other “twin”, unexpected inheritance patterns can happen. This is when a twin pregnancy combines into a single fetus with a combination of both twins’ sets of DNA. But their sperm/eggs will still have the recipient’s original DNA and blood type. A bone marrow transplant recipient will have the blood type of the donor. If the DNA in the blood isn’t the same as the DNA in the sperm/eggs, a child might inherit an unexpected type.Ĭhimerism can happen in a few different ways: Rare exceptions to the blood type inheritance rules ChimerismĪ chimera is a person who has two different sets of DNA, from two different individuals. See below for some of the ways to break the blood type inheritance rules. Like with everything in biology, sometimes there are exceptions to the patterns mentioned above. Don’t jump to conclusions, exceptions can happen While blood type was often used during the early 1900s as a rudimentary paternity test, today more reliable tests like paternity tests or ancestry-type tests should be used to confirm or reject parentage. The blood type inheritance pattern is very predictable. Or donate blood to your local blood bank, as they’ll generally send you your blood type information afterwards. In any case, ask your health care provider for a blood type test. This is one way that two negative-type parents could have a positive-type child. Sometimes a test won’t detect that someone is actually Rh+, incorrectly labeling them as Rh. And sometimes people have an error in their test results, due to some mixup in the lab.Īn especially common blood typing error is incorrectly determining someone’s Rh type. It’s actually very common for people to misremember their blood type. Humans make a lot of mistakes, so this is always worth double checking before you go any farther. Help! My child’s blood type doesn’t make sense 1. Why are Rh blood tests sometimes inaccurate?. ![]() Why do some Rh negative moms have pregnancy complications?.How do I have Rh negative-type blood, when both my parents are positive?.Why do children sometimes have different blood types from their parents?.These two things are determined by two different genes and are inherited separately. Note that the ABO part is in a separate table from the +/- part. Here are a child’s possible blood types for any two parents: ![]() In the vast majority of cases, blood type follows a predictable inheritance pattern.
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