| Cross | Genes | Typical phenotype ratio | Notes |
|---|---|---|---|
| Aa × Aa | 1 | 3 : 1 (dominant : recessive) | Complete dominance monohybrid cross. |
| Aa × aa | 1 | 1 : 1 | Test cross for a single gene. |
| AaBb × AaBb | 2 | 9 : 3 : 3 : 1 | Independent assortment, two genes, dominance model. |
- Gamete probability: each heterozygous gene contributes alleles with probability 1/2; homozygous contributes 1.
- Product rule: for independent genes, a gamete probability is the product of per-gene allele probabilities.
- Offspring probability: P(offspring genotype) = Σ [ P(gamete₁) × P(gamete₂) ] across all gamete pairs that produce it.
- Phenotypes: mapped from genotypes using the chosen inheritance model (complete dominance, incomplete dominance, or codominance).
- Select 1 gene for monohybrid or 2 genes for dihybrid.
- Enter each parent genotype using 2 letters per gene (e.g., AaBb).
- Choose inheritance model and set phenotype labels for each gene.
- Press Calculate inheritance to view Punnett square, ratios, and distributions.
- Use targets to get the probability of one genotype or phenotype.
- Download CSV or PDF for saving and sharing.
1) What genotype format should I enter?
Use two letters per gene. For one gene: Aa. For two genes: AaBb. Uppercase and lowercase represent different alleles.
2) Does this handle independent assortment?
Yes. Two-gene crosses assume genes assort independently, so gamete probabilities follow the product rule across genes.
3) What is the difference between dominance and incomplete dominance?
In complete dominance, Aa shows the dominant trait. In incomplete dominance, Aa shows an intermediate trait between AA and aa.
4) How does codominance work here?
Codominance treats the heterozygote as its own phenotype label. Set the Aa label to a “both expressed” description.
5) Why do my phenotype targets not match?
Targets must match the output text exactly. Copy a phenotype label from the results table and paste it into the target box.
6) Can I use different letters than A and B?
Yes. Any letters are accepted. Keep each gene as a two-letter pair, and keep both parents consistent for the same gene.
7) What does the PDF include?
The PDF contains a clean summary of the cross, genotype percentages, phenotype percentages, optional targets, and a timestamp for recordkeeping.