Blood Type / Genotype Calculator
Determine the probabilities of ABO blood types and Rh factor (+/-) inheritance for children based on parents' genotypes.
Parental Blood Types & Genotypes
Select the specific ABO and Rh factor genotype details for each parent.
Parent 1
Parent 2
ABO Punnett Grid
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Rh Factor Punnett Grid
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Offspring Blood Type Probabilities
Phenotype (Blood Group & Rh)
Genotype Breakdown
Expert Tip
ABO blood types follow codominance (alleles A and B) and recessive inheritance (allele O). The Rh factor (+/-) follows simple dominant (+) and recessive (-) inheritance.
Methodology & Equations
ABO Blood Group Inheritance
The ABO gene has three primary alleles:
- **IA:** Codes for antigen A (dominant to i).
- **IB:** Codes for antigen B (dominant to i).
- **i (O):** Codes for no antigen (recessive to IA and IB).
This results in four phenotypes: A (AA, AO), B (BB, BO), AB (AB), and O (OO).
Rh Factor (+/-) Inheritance
The Rhesus factor is determined by the presence or absence of the D antigen:
- **D (Rh+):** Dominant allele (represented as + or D).
- **d (Rh-):** Recessive allele (represented as - or d).
Hence, Rh-positive individuals can be DD or Dd, while Rh-negative individuals must be dd.
Predicting Offspring Blood Type: Step-by-Step
Let's look at an example crossing Parent 1 (AO, Dd - Type A+) and Parent 2 (BO, dd - Type B-):
Create ABO Punnett Square
Parent 1 alleles: A, O. Parent 2 alleles: B, O.
Offspring: AB (25%), AO (25% Type A), BO (25% Type B), OO (25% Type O).
Create Rh Factor Punnett Square
Parent 1 alleles: D, d. Parent 2 alleles: d, d.
Offspring: Dd (50% Rh+), dd (50% Rh-).
Combine the Probabilities
Multiply the ABO percentages by the Rh percentages (independent assortment):
- **AB+:** 25% AB × 50% Rh+ = 12.5%
- **AB-:** 25% AB × 50% Rh- = 12.5%
- **A+:** 25% A × 50% Rh+ = 12.5%
- **A-:** 25% A × 50% Rh- = 12.5%
- **B+:** 25% B × 50% Rh+ = 12.5%
- **B-:** 25% B × 50% Rh- = 12.5%
- **O+:** 25% O × 50% Rh+ = 12.5%
- **O-:** 25% O × 50% Rh- = 12.5%
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