Each parent passes on one of their two ABO genes and one of two Rh genes. Because a parent who is type A or B may carry a hidden O, several types are often possible.
Possible ABO types: O, A, B, AB
Your answer
Possible ABO typesO, A, B, AB
Possible Rhpositive or negative
Not possible
None ruled out
Rare variants (such as the Bombay phenotype or cis-AB) can break these rules, so blood type alone can’t prove or disprove parentage.
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How we worked it out
Updated as you change the numbers.
A can be AA or AO, B can be BB or BO, AB is AB and O is OO. Every pairing of one gene from each parent gives the possible child types.
Rh: two negative parents can only have a negative child; otherwise either is possible.
Method and assumptions
A and B are co-dominant and both dominate O. Rh positive dominates Rh negative.
Questions
Can parents with A and B blood have an O child?
Yes, if both carry a hidden O gene. Their child can be O, A, B or AB.
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