AB Blood Father, O Blood Child: Understanding Blood Type Inheritance
No. A father with type AB blood cannot have a biological child with type O blood, regardless of the mother's blood type. This is a fundamental rule of ABO genetics.
Genetic Basis
- Father (Type AB): Genotype IAIB. He carries one A allele and one B allele. He has no O allele to transmit.
- Mother (Type O): Genotype ii. She can only transmit an O allele.
Possible Offspring Genotypes
| Father's Gamete | Mother's Gamete | Child Genotype | Child Phenotype |
|---|
| IA | i | IAi | Type A |
| IB | i | IBi | Type B |
Type AB (IAIB) is possible if mother contributes A or B (i.e., mother is A, B, or AB).
Type O (ii) is impossible because father cannot contribute i.
Rare Exceptions (Not Standard Inheritance)
- Chimerism: Father is a fusion of two zygotes; gonads derived from O-genotype line. Extremely rare; <100 cases documented.
- Cis-AB allele: Single allele encodes both A and B antigens. Father would phenotype as AB but could transmit O if genotype is cis-AB / i. Rare, mostly East Asian populations.
- Genotyping error / sample mix-up.
- Non-paternity.
Clinical Relevance
- ABO exclusion is used in forensic paternity testing (along with STR loci).
- If AB father and O mother have O child → investigate lab error or non-paternity before assuming rare genetics.
- Blood type ≠ paternity proof; only exclusion.
Standard Mendelian genetics is unequivocal: AB × O → A or B children only.
Blood Disorders - Related Articles
