Dihybrid Cross Calculator
Choose a one-gene cross for a classic Punnett square, a two-gene cross for a dihybrid cross, or a three-gene cross for a trihybrid cross (such as AaBbCc × AaBbCc), then select each parent's genotype to calculate offspring genotype and phenotype probabilities, assuming independent assortment and complete dominance.
Last updated: September 25, 2026
Frequently asked questions
Can this calculate a trihybrid cross like AaBbCc × AaBbCc?
Yes. Choose "Three genes (trihybrid cross)" and set each parent's genotype at genes 1, 2, and 3. For AaBbCc × AaBbCc each parent makes 8 different gametes, giving 8 × 8 = 64 offspring combinations and the classic 27:9:9:9:3:3:3:1 phenotype ratio. It is the same tool as the one- and two-gene modes, so there is no separate trihybrid page.
Is this the same as a Punnett Square Calculator?
Yes. Choose "One gene" to get a classic single-gene Punnett square (a 2x2 grid of offspring combinations), or "Two genes" for a dihybrid cross (a 4x4 grid). Both modes live in this one calculator instead of separate pages.
What does 'independent assortment' mean and why does it matter here?
Independent assortment is the Mendelian principle that alleles for different genes are inherited independently of each other, which holds true when the two genes are on different chromosomes (or far apart on the same one). This calculator assumes independent assortment - if the two genes were closely linked on the same chromosome, they'd tend to be inherited together more often than this model predicts, which is called genetic linkage.
How is this different from the Allele Frequency Calculator?
The Allele Frequency Calculator works backward from real observed genotype counts in a population sample to calculate allele frequencies (p and q) for a single gene. This Dihybrid Cross Calculator instead works forward from two known parent genotypes across two genes to predict possible offspring outcomes and their probabilities - they answer different questions using different inputs.
How is this different from a Hardy-Weinberg calculation?
Hardy-Weinberg calculations predict genotype frequencies in a large population at equilibrium, given allele frequencies, for a single gene. A dihybrid cross instead predicts individual offspring outcomes from two specific known parents across two genes - one is a population-level equilibrium model, the other is an individual-cross probability model, and they're used for different kinds of genetics questions.
Why does the calculator show 4 possible gametes for a heterozygous parent at both genes?
A parent heterozygous at both genes (like AaBb) can pass on any combination of one allele from each gene - AB, Ab, aB, or ab - assuming independent assortment, giving 4 equally likely gamete types. A parent homozygous at one or both genes produces fewer distinct gamete types, since a homozygous locus can only pass on one allele.
What does 'complete dominance' mean for the phenotype ratios shown?
Complete dominance means one allele fully masks the other in a heterozygote, so a genotype like Aa looks identical to AA for that trait - only the homozygous recessive genotype (aa) shows the recessive phenotype. This calculator's phenotype ratios assume complete dominance at both genes; traits with incomplete dominance or codominance would show additional intermediate or blended phenotypes not reflected here.
Can I use this for real gene pairs, like predicting an actual pet's or plant's offspring traits?
It can be a useful educational approximation if you're confident the two genes assort independently and show complete dominance, but real biology often includes complications like linkage, incomplete dominance, or gene interactions that this simplified model doesn't capture - for anything with real consequences (breeding decisions, genetic counseling, etc.), consult a qualified geneticist or relevant specialist rather than relying solely on this tool.