Blood type inheritance
Work out which ABO blood types and probabilities a child can inherit from two parents, and reverse-look-up which parent pairings can produce a given child blood type.
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Inheritance result
Possible blood types with percentages.
Enter blood types to calculate
Possible types: 0 · Top probability: 0 · Pairings: 0
What this tool does
- Answer questions like 'can an A and a B parent have an O child' with concrete probabilities.
- Reverse lookup: given an O child, list every parent blood-type pairing that could produce it.
- Check a child's biology homework — draw the 4-cell Punnett square by hand, then verify it here.
- Push back on 'the blood type proves it is not my child' claims: ABO can only exclude, never confirm.
Example
Input
A,B
Output
父母血型：A × B 子女可能出现：A / B / AB / O A 型：18.75% B 型：18.75% AB 型：56.25% O 型：6.25% 说明：父母各给一个等位基因，等位组合等权统计（共 4 种），因此概率都是 25% 的整数倍。 ABO 血型只能用来排除亲子关系，不能证明亲子关系；法律用途请做 DNA 鉴定。
ABO blood types come from the A, B and O alleles with O recessive; probabilities weight every genotype pairing equally.
Frequently asked questions
How are the probabilities calculated?
Everyone carries two alleles: AA/AO is type A, BB/BO type B, AB is AB and OO is O. Each parent passes on one allele. The tool weights every genotype pairing and allele combination equally, then folds them back into phenotypes. A×B gives A 18.75%, B 18.75%, AB 56.25% and O 6.25%, summing to exactly 100%.
Why can A and B parents have an O child?
Because type A may be AO and type B may be BO; if both pass the O allele the child is OO. That is also why 'neither parent is O but the child is' is not a contradiction.
Can two AB parents have an O child?
No. AB has only one genotype, AB, with no O allele to pass on, so the child can only be A, B or AB at 25%, 25% and 50%.
Can blood types be used for paternity testing?
No. Blood types can only rule out certain pairings (an O parent cannot have an AB child, for example), but most pairings allow several child types, so they cannot confirm a relationship. Use DNA testing for legal or medical purposes.
Why are the probabilities multiples of 25%?
Because the unit of counting is the allele combination: a genotype pair yields at most four combinations. When a phenotype has two genotypes (A = AA or AO) they are counted separately, so the finest step is 6.25% (1/16) and the actual values depend on how many genotypes each parent may have.
Is anything uploaded?
No, everything is computed locally in the browser from fixed rules.
Keywords：血型遗传blood typeABO血型计算子女血型基因型亲子血型