Trihybrid Cross Punnett Square Calculator

A trihybrid cross follows inheritance at three gene loci at the same time. A genotype such as AaBbCc describes an individual that is heterozygous at all three loci. Under complete dominance, an uppercase allele produces the dominant phenotype when one or two copies are present, while the recessive phenotype appears only when both copies are lowercase. The calculator accepts three adjacent allele pairs for each parent and keeps the gene letters supplied by the user. Gametes receive one allele from each locus. An AaBbCc parent can therefore produce eight gamete types: ABC, ABc, AbC, Abc, aBC, aBc, abC, and abc. Crossing two such parents creates eight rows by eight columns, or 64 equally likely Punnett-square cells. The calculator combines corresponding alleles, places uppercase alleles first within each pair, counts repeated offspring genotypes, and reports each count over the total number of cells. Homozygous loci produce fewer distinct gamete types, so their displayed square can be smaller without changing the genetic logic. Phenotype classes group genotypes that have the same dominant or recessive expression at each locus. The output uses D for a locus with at least one dominant allele and r for a homozygous recessive locus. For the classic AaBbCc by AaBbCc cross, independent assortment and complete dominance produce eight phenotype classes, including DDD at 27 of 64 offspring and rrr at 1 of 64. Genotype ratios are more detailed because AA, Aa, and aa remain distinct even when AA and Aa share a phenotype. This Mendelian model assumes autosomal loci that assort independently, equal gamete viability, random fertilization, complete penetrance, and complete dominance. Linked genes, recombination distance, sex linkage, lethal alleles, segregation distortion, epistasis, incomplete dominance, codominance, environmental effects, and small sample sizes can change observed outcomes. A Punnett square describes probabilities for each conception, not a guaranteed distribution in a family or experiment. Use the calculator for education and simple genetic models, state the inheritance assumptions clearly, and use linkage or pedigree methods when the biological system does not meet those assumptions.