Blood Type Calculator

Human blood grouping is governed by the ABO gene system, which features three primary alleles: $I^A$, $I^B$, and $i$. Every individual inherits two alleles—one from each parent. Alleles $I^A$ and $I^B$ are codominant, while $i$ is recessive. This interaction creates four major phenotypes: Type A ($I^A I^A$ or $I^A i$), Type B ($I^B I^B$ or $I^B i$), Type AB ($I^A I^B$), and Type O ($ii$). Additionally, the Rhesus (Rh) factor operates on dominant-recessive inheritance, where the Rh-positive allele (R) completely masks the recessive Rh-negative allele (r), determining whether your blood type is positive or negative.

Let us calculate the genetic probability for a child whose mother has heterozygous Type A blood ($I^A i$) and whose father has heterozygous Type B blood ($I^B i$). First, we map out a Punnett square combining the mother's alleles ($I^A$ and $i$) with the father's alleles ($I^B$ and $i$). This yields four equally likely combinations: $I^A I^B$ (Type AB), $I^A i$ (Type A), $I^B i$ (Type B), and $ii$ (Type O). Consequently, this couple has a 25% chance of producing a child with Type AB, Type A, Type B, or Type O blood respectively, demonstrating how two parents can conceive a child with any of the four major blood groups.

When evaluating blood type probabilities, remember that phenotype does not always reveal genotype. For instance, an individual with Type A blood could carry either an $I^A I^A$ (homozygous) or $I^A i$ (heterozygous) gene pair, which drastically alters offspring probabilities. Furthermore, always account for the Rh factor separately from the ABO grouping to ensure comprehensive family planning insights. Lastly, consult a certified genetic counselor or medical professional for clinical-grade family health evaluations.