How this calculator works
Three unlinked two-allele loci can produce eight gamete combinations per heterozygous parent. The calculation enumerates 64 pairings and groups the resulting 27 possible unordered genotypes. Phenotype groups use complete dominance at each locus. This is useful for checking three-trait crosses, but linkage, epistasis and unequal viability can invalidate the independent model.
Formula
Each gamete pairing has probability 1/(2^loci × 2^loci). Genotype probability = matching pairings/total pairings. Independent-locus probabilities multiply.
Worked example
AaBbCc crossed with AaBbCc gives all three dominant phenotypes with probability 27/64 and aabbcc with probability 1/64. AABBCC crossed with aabbcc gives AaBbCc in every pairing.
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Frequently asked questions
Why does a trihybrid square have 64 pairings?
A triple heterozygote has eight equally likely gamete combinations. Eight times eight produces 64 pairings.
What is the all-dominant probability?
For two triple heterozygotes under complete dominance and independence, it is (3/4) cubed, or 27/64.
Can a table predict exact offspring counts?
No. It predicts probabilities. Real counts vary through random sampling and biological effects beyond the model.