🌿 Dihybrid Cross Calculator
Explore genotype and phenotype ratios for crosses involving two independent genes.
Use two genes with two alleles each, e.g., AaBb or AABb.
How to Use This Calculator
Enter parental genotypes
Type the genotype for each parent using two genes, such as AaBb. Both parents must represent the same genes in the same order.
Generate Punnett square
Click the calculate button to create the 4×4 Punnett square, genotype counts, and phenotype ratios.
Interpret the results
Use the genotype and phenotype summaries to predict offspring probabilities and Mendelian ratios.
Formula
Gametes = combinations of alleles from each gene
Example: AaBb produces gametes AB, Ab, aB, ab
Punnett outcome = gamete (parent 1) × gamete (parent 2)
Count each genotype in the Punnett grid to determine ratios. A classic AaBb × AaBb cross yields the 9:3:3:1 phenotype ratio under complete dominance and independent assortment.
Full Description
A dihybrid cross examines the inheritance of two genes simultaneously. Each parent contributes one allele per gene to every gamete, producing four potential gametes (AB, Ab, aB, ab) in heterozygous parents. The Punnett square enumerates all possible combinations between parental gametes.
When both loci follow Mendelian dominance and segregate independently, the Fâ‚‚ generation exhibits the canonical 9:3:3:1 phenotype ratio. Deviations from this ratio can signal linkage, epistasis, or other non-Mendelian interactions.
Frequently Asked Questions
Why must alleles be written together (e.g., AaBb)?
The calculator expects a four-letter string representing two genes in sequence. This ensures gametes are generated correctly for each independent gene.
How are dominant vs. recessive traits handled?
Dominant alleles are assumed to be uppercase letters. Any genotype containing at least one uppercase allele for a gene is treated as expressing the dominant phenotype.
Can this tool handle linked genes?
This calculator assumes independent assortment. Linked genes require recombination frequencies to predict offspring ratios, which are not included here.
What if parents are homozygous for one gene?
Homozygous alleles (AA or aa) are valid. The Punnett square will reflect the limited gamete combinations and resulting offspring ratios.