Blood Type Inheritance
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Pick both parents' blood types and see which types a child can have, and which are impossible. The genetics is one allele pair: A and B are dominant, O recessive, so type A may be AA or AO and type B may be BB or BO. Each parent contributes one allele and the child's type follows. "Can they have an O child?" is the question that comes up most — two AB parents cannot, while an A and a B parent can. The percentage column rests on an assumption that has to be stated: the tool does not know your population, so it treats every genotype within a phenotype as equally likely (type A as half AA, half AO). The can/cannot split is the reliable part; the percentages are a reference value under that assumption.
Features
- Possible and impossible child types, listed separately
- Genotypes for each type (AA, AO, BB, BO, AB, OO)
- Percentages under the stated equal-genotype assumption
- The parents' genotypes are shown too, so the reasoning can be checked
- One dropdown per parent: four entries (A, B, AB, O), nothing to type
- The O entry is labelled "the letter O", so it cannot be confused with zero
How to use
- Pick the father's blood type, then the mother's
- Possible types and percentages appear first
- Impossible types get their own section — that is the part people come for
- The percentage assumption is written at the end of the result
FAQ
- Can two AB parents have an O child?
- No. AB has a single genotype, so any child receives either an A or a B and must show as A, B or AB. Conversely, an A and a B parent can have an O child (when both are AO / BO) — one of the most common misconceptions.
- Why are the percentages only an assumption?
- Because "type A" covers both AA and AO, and their proportions depend on population gene frequencies — the tool does not know your population, so it assumes half and half. Change the region and the numbers change. The can/cannot conclusions depend only on the rules of inheritance and are reliable; the percentages depend on the assumption and are a reference.
- Can the O in a blood type be mistyped as a zero?
- Not here — the blood type is picked from a dropdown, and the O entry reads "Type O (the letter O)", so there is nothing to type and nothing to mistype. It is worth knowing anyway: in some fonts the two are nearly identical, and an O type is not a "0 type".
- Can this be used for paternity testing?
- No. Blood types can rule combinations out (two O parents cannot have an AB child) but cannot confirm a relationship — many different parent pairs produce the same child type. Paternity testing needs DNA testing at an accredited laboratory.
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