What is a dihybrid cross?

A dihybrid cross is a genetic cross between two parents that differ in two traits, each controlled by a separate gene locus. The Dihybrid Cross Calculator shows all possible offspring genotype and phenotype combinations.

What is the classic 9:3:3:1 ratio in a dihybrid cross?

When both parents are heterozygous (e.g. AaBb × AaBb), the Dihybrid Cross Calculator shows that offspring phenotypes follow a 9:3:3:1 ratio — 9 dominant for both traits, 3 dominant for trait 1 only, 3 dominant for trait 2 only, and 1 recessive for both.

How do I enter genotypes in the Dihybrid Cross Calculator?

Type a 4-letter genotype such as AaBb, AABB, aabb, or AaBB. Each pair of letters must represent the same gene (e.g. A and a for locus 1, B and b for locus 2). Uppercase means dominant; lowercase means recessive.

Can the Dihybrid Cross Calculator handle homozygous parents?

Yes. You can enter any valid combination such as AABB × aabb or AABb × aaBb. The calculator generates the correct gametes and Punnett square for any valid dihybrid genotype.

No. All calculations happen in your browser; nothing is sent to a server.

Dihybrid Cross Calculator

How to Use Dihybrid Cross Calculator

The Dihybrid Cross Calculator lets you analyze two-gene Mendelian inheritance in seconds.

Parent 1 Genotype — Enter a 4-letter genotype such as AaBb or AABB. Each consecutive pair of letters represents one gene locus.
Parent 2 Genotype — Enter the second parent's genotype in the same format (e.g. AaBb, aabb).
Results — The Dihybrid Cross Calculator instantly displays the 4×4 Punnett square, phenotype ratio, and all genotype frequencies.

Both uppercase and lowercase letters are meaningful: uppercase indicates a dominant allele, lowercase indicates a recessive allele. The Dihybrid Cross Calculator validates input automatically and flags invalid genotypes.

Formula & Theory — Dihybrid Cross Calculator

The Dihybrid Cross Calculator applies Mendel's Law of Independent Assortment. When two gene loci are on separate chromosomes (or far apart on the same chromosome), the alleles at each locus segregate independently.

Gamete generation:

Each parent with genotype AaBb can produce four types of gametes:

AB, Ab, aB, ab

The probability of each gamete is equal (1/4) when both loci are heterozygous.

Punnett square construction:

        AB    Ab    aB    ab
AB    AABB  AABb  AaBB  AaBb
Ab    AABb  AAbb  AaBb  Aabb
aB    AaBB  AaBb  aaBB  aaBb
ab    AaBb  Aabb  aaBb  aabb

Phenotype determination:

A locus expresses the dominant phenotype if at least one allele is dominant (uppercase). The classic AaBb × AaBb cross yields a 9:3:3:1 phenotype ratio from 16 total offspring combinations.

Assumptions

The Dihybrid Cross Calculator assumes complete dominance at each locus and independent assortment between loci. It does not model incomplete dominance, codominance, or genetic linkage.

Use Cases for Dihybrid Cross Calculator

The Dihybrid Cross Calculator is widely used in biology education and research:

Genetics homework — Quickly verify expected offspring ratios for any two-gene cross problem.
Exam preparation — Practice predicting phenotype and genotype distributions for Mendelian genetics questions using the Dihybrid Cross Calculator.
Lab report verification — Compare observed offspring ratios against the theoretical values generated by the Dihybrid Cross Calculator.
Teaching tool — Instructors can use the Dihybrid Cross Calculator to demonstrate independent assortment with different parental genotype combinations.
Research baseline — Establish expected Mendelian ratios before testing for deviations such as linkage or epistasis.

Whether you are a high school student learning Mendel's laws for the first time or an undergraduate verifying chi-square results against theoretical predictions, the Dihybrid Cross Calculator provides fast, reliable dihybrid cross analysis in your browser.