Determine the possible blood types of children based on both parents' blood types using ABO blood group genetics. Shows all possible genotype combinations and their probabilities.
The ABO blood group system, discovered by Karl Landsteiner in 1901 (Nobel Prize 1930), is one of the most important genetic systems in medicine. Blood type determines whose blood you can receive (transfusion compatibility) and donate to, who can safely receive your organs (transplantation), and provides one piece of evidence in paternity testing. The system follows classical Mendelian inheritance with one important twist: codominance between A and B alleles produces the AB blood type when both are inherited.
Blood type inheritance follows three alleles at one gene location: I^A (codes for A antigen), I^B (codes for B antigen), and i (codes for neither). Each parent contributes one allele to the child. I^A and I^B are codominant (both expressed when together = AB). Both are dominant over i (i is recessive, requires both copies for type O expression). The four possible blood phenotypes (A, B, AB, O) result from six possible genotype combinations: I^AI^A or I^Ai (both type A), I^BI^B or I^Bi (both type B), I^AI^B (AB), or ii (O).
This calculator predicts possible offspring blood types from parent blood types. Use it for: understanding inheritance patterns, genealogy research, family planning curiosity, paternity considerations (blood type alone cannot prove paternity but can rule it out), and biology education. Important context: blood type prediction shows POSSIBLE outcomes and probabilities, not definitive answers. Because some blood types have multiple possible genotypes (Type A could be I^AI^A or I^Ai), the exact possibilities depend on genotypes (not always determinable from phenotype alone). For paternity testing: blood type can exclude paternity in some cases (Type O child can't have AB father) but DNA testing required for positive paternity confirmation. For medical decisions (transfusion, transplant): actual blood typing performed in lab, not predicted from family history.
Mother Type AB, Father Type O. Mother genotype: I^A I^B (only possible genotype for AB) Father genotype: i i (only possible genotype for O) Punnett square: I^A I^B i I^A i (A) I^B i (B) i I^A i (A) I^B i (B) Offspring possibilities: 50% Type A (I^A i) 50% Type B (I^B i) 0% Type AB 0% Type O Counterintuitive: AB × O parents can have A or B children but NEVER AB or O children. AB parent must give either I^A or I^B; O parent must give i. Combination always heterozygous (one A or B antigen + i). For paternity test: if claimed child is Type O, AB mother and O father is impossible. Test excludes this paternity. If child is Type AB, AB mother and O father also impossible (O father can't contribute I^A or I^B).
Mother Type A (genotype unknown — could be I^AI^A or I^Ai), Father Type B (could be I^BI^B or I^Bi). If both parents heterozygous (I^A i and I^B i): I^B i I^A I^A I^B (AB) I^A i (A) i I^B i (B) i i (O) ALL FOUR blood types possible: 25% A, 25% B, 25% AB, 25% O. If mother homozygous (I^A I^A) and father heterozygous (I^B i): I^B i I^A I^A I^B (AB) I^A i (A) I^A I^A I^B (AB) I^A i (A) Only A and AB possible: 50% A, 50% AB. Without knowing exact parent genotypes, can't predict exact probabilities. Calculator typically shows range of possibilities. Real-world application: in families where parents are A and B, offspring can be any of four types. This sometimes surprises people who expect children to "blend" parent types.
Mother Type A. Child Type B. Three potential fathers: Bob (Type O), Carlos (Type A), David (Type B). Mother Type A genotypes: I^A I^A or I^A i Child Type B genotypes: I^B I^B or I^B i Child has I^B allele. Where did it come from? Mother is Type A (no I^B alleles), so I^B must come from father. Bob: Type O (ii) — has no I^B alleles. CANNOT be father. Excluded. Carlos: Type A (I^A I^A or I^A i) — has no I^B alleles. CANNOT be father. Excluded. David: Type B (I^B I^B or I^B i) — has I^B alleles. POSSIBLE father. Blood type evidence: only David could be biological father based on ABO inheritance. However: this doesn't prove David IS the father. Any Type B or Type AB man could be biological father based on blood type alone. DNA testing required for positive identification. Historical use: blood types used in early 20th century for paternity disputes (could only exclude, never confirm). DNA testing now standard.
Use this calculator for understanding inheritance patterns, genealogy research, family planning curiosity, paternity exclusion analysis (cannot confirm, only exclude), or biology education.
Pair with punnett-square (general Mendelian inheritance), hardy-weinberg (population genetics), and population-growth (broader genetics applications).
Important blood type considerations:
1. **Cannot definitively confirm paternity.** Blood type can rule out impossible paternity but cannot positively identify. DNA testing required for confirmation.
2. **Parent genotypes often unknown.** Type A could be I^AI^A or I^Ai; outcomes depend on specific genotype. Calculator shows range of possibilities.
3. **Some combinations exclude offspring types.** O × AB cannot produce O or AB children. O × O can only produce O. These are firm genetic rules.
4. **Codominance differs from blending.** A and B don't "average" — when both present, both expressed (AB). Many people misunderstand this aspect of genetics.
5. **Rh factor separate inheritance.** Rh+ dominant over Rh-. This calculator focuses on ABO; consider Rh separately for complete picture.
6. **Population variation matters.** Type frequencies vary by ethnicity and geography. Don't assume population averages for specific families.
7. **Rare blood types exist.** Beyond ABO/Rh, many minor blood group systems matter for transfusion. Some individuals have very rare types requiring specialized donors.
8. **Medical decisions need lab confirmation.** Predicted blood type insufficient for transfusion or surgery. Always lab-tested actual type for medical use.
9. **Transfusion compatibility critical.** O- universal donor, AB+ universal recipient. Type-specific transfusion preferred when possible.
10. **Hemolytic disease risk.** Rh- mother with Rh+ father can have Rh+ baby. Sensitization in first pregnancy causes attack on subsequent Rh+ pregnancies. RhoGAM injection prevents.
11. **Blood type doesn't determine personality.** Common Japanese belief associates blood type with character traits. No scientific basis.
12. **Bombay phenotype exception.** Extremely rare (~1 in 1 million in Europe; higher in some Asian populations) — appears Type O but actually lacks H antigen precursor. Can complicate transfusion compatibility.
Generate a monohybrid Punnett square showing genotype and phenotype ratios.
Calculate allele and genotype frequencies using Hardy-Weinberg equations.
Model exponential and logistic population growth over time.
Calculate bacterial generation (doubling) time from growth data.
Possible Types
Type A, Type B, Type AB, Type O
# Outcomes
4
| Parameter | Value |
|---|---|
| Parent 1 Blood Type | Type A |
| Parent 1 Possible Genotypes | IA/IA or IA/i |
| Parent 2 Blood Type | Type B |
| Parent 2 Possible Genotypes | IB/IB or IB/i |
| Total Combinations | 16 |
| Type A Probability | 18.8% |
| Type B Probability | 18.8% |
| Type AB Probability | 56.3% |
| Type O Probability | 6.3% |
| Possible Offspring Types | Type A, Type B, Type AB, Type O |