Calculator Form
Formula Used
Probability of a gamete = Probability of allele from gene 1 × Probability of allele from gene 2
Probability of offspring genotype = Probability of parent 1 gamete × Probability of parent 2 gamete
Genotype frequency = Sum of all matching Punnett square cell probabilities
Phenotype frequency = Sum of all genotype probabilities producing the same visible trait combination
For the classic cross AaBb × AaBb, each parent forms AB, Ab, aB, and ab gametes equally. That creates sixteen outcomes and the familiar phenotype ratio of 9:3:3:1 under complete dominance and independent assortment.
How to Use This Calculator
- Enter Parent 1 and Parent 2 genotypes in four-letter format, such as AaBb.
- Type the dominant and recessive phenotype names for each gene.
- Click Generate Dihybrid Cross to calculate gametes and offspring outcomes.
- Review the result block shown above the form and directly under the header.
- Study the Punnett square, genotype table, phenotype table, and the chart.
- Use the CSV or PDF buttons to export the calculated results.
Example Data Table
| Example | Parent 1 | Parent 2 | Trait 1 | Trait 2 | Expected Phenotype Ratio |
|---|---|---|---|---|---|
| Mendelian Example | AaBb | AaBb | Round / Wrinkled | Yellow / Green | 9 : 3 : 3 : 1 |
| Mixed Homozygous Example | AABb | aaBb | Tall / Short | Purple / White | 3 : 1 |
| Partial Heterozygous Example | Aabb | AaBb | Dominant A / Recessive a | Dominant B / Recessive b | 3 : 3 : 1 : 1 |
FAQs
1) What is a dihybrid cross?
A dihybrid cross tracks inheritance for two different genes at the same time. It helps predict genotype combinations, phenotype combinations, and expected probability patterns in offspring.
2) What does a Punnett square show?
A Punnett square lists parental gametes on two axes and combines them in each cell. Every cell represents one possible offspring genotype and its probability.
3) Why are there often sixteen boxes?
In the common AaBb × AaBb cross, each parent produces four gametes. Four gametes by four gametes creates sixteen possible allele combinations in the grid.
4) Can this calculator handle homozygous parents?
Yes. It works with homozygous, heterozygous, and mixed two-gene genotypes such as AABB, AaBb, aaBb, or Aabb, as long as each genotype uses four valid alleles.
5) Does it calculate both genotype and phenotype ratios?
Yes. The result section shows the Punnett square, genotype frequencies, phenotype frequencies, simplified ratios, and the most likely genotype and phenotype.
6) How are gametes determined?
One allele from the first gene combines with one allele from the second gene. The calculator generates every possible gamete and counts repeated outcomes automatically.
7) Why might my result differ from 9:3:3:1?
The 9:3:3:1 ratio appears only in the classic AaBb × AaBb case under complete dominance and independent assortment. Different parent genotypes produce different ratios.
8) Can I use the exports for teaching or assignments?
Yes. The CSV file is useful for spreadsheets, and the PDF file gives a ready summary for lessons, homework review, class notes, or lab reports.