Original instructional diagram for The 9:3:3:1 Ratio Depends on Independent Assortment. Values, when shown, are illustrative; clinical images do not recommend a dose.
Check whether the loci can be treated independently
The familiar two-locus phenotype ratio requires independent assortment and a particular parental cross. Linkage or a different genotype changes the outcome. Do not choose a ratio from memory before checking what each parent can transmit.
Use Dihybrid Cross Calculator - Punnett Square to work through these inputs while keeping the displayed assumptions in view.
Separate genotype and phenotype summaries
Several genotypes can share a dominant phenotype under complete dominance. A count of visible trait categories therefore need not equal the number of genotype categories. Use the two result tables for their respective questions rather than treating them as competing answers.
This question belongs to the Genetics calculators group within Biology calculators.
Read the calculation on its stated basis
Enumerate each parent’s gametes, combine alleles at each locus, then count genotype and complete-dominance phenotype probabilities.
Assumes independent assortment and complete dominance. Does not model linkage, penetrance, viability effects or an individual clinical genetic risk.
A model is useful only within its assumptions. The result describes the input population or cross; it does not supply missing biological information or replace an appropriate genetic assessment.
Keep related questions separate
Punnett Square Calculator addresses a related part of the measurement or interpretation task. Check its own method before carrying a value from one tool to the other.
For a related perspective, read A Punnett Square Gives Per-Offspring Probabilities, Not a Family Guarantee.
For tools in other subjects, return to GreenCalc. Keep the calculator result with its assumptions rather than using a link or a matching unit as evidence that two models are interchangeable.
By GreenCalc · Updated 2026-11-05