Dihybrid Cross Punnett Square
Calculate dihybrid cross Punnett square genotype and phenotype ratios for two traits with four alleles. Free online genetics calculator with Punnett square grid, charts, and probability breakdowns.
Mother's Genotype
Father's Genotype
About This Calculator
The Dihybrid Cross Punnett Square Calculator helps genetics students, teachers, and researchers predict the probability of offspring inheriting two different traits. A dihybrid cross tracks the inheritance patterns of two genes simultaneously, demonstrating Mendel's law of independent assortment. This free online genetics tool generates a complete 4×4 Punnett square, calculates all 9 possible genotype frequencies, and determines both genotypic and phenotypic ratios.
The calculator works by first determining all possible gamete combinations for each parent using the FOIL method (First, Outer, Inner, Last). For a parent with genotype AaBb, the four possible gametes are AB, Ab, aB, and ab. These gametes are arranged along the top and left side of a 4×4 grid. Each cell is filled by combining one maternal gamete with one paternal gamete, yielding 16 possible offspring genotypes. The calculator then counts the frequency of each of the 9 distinct genotypes and groups them into 4 phenotype categories based on dominant and recessive allele expression.
In the classic dihybrid cross between two heterozygous parents (AaBb × AaBb), the phenotypic ratio follows Mendel's 9:3:3:1 pattern: 9/16 offspring show both dominant traits (A_B_), 3/16 show the first dominant trait and second recessive trait (A_bb), 3/16 show the first recessive trait and second dominant trait (aaB_), and 1/16 show both recessive traits (aabb). This ratio is a cornerstone of Mendelian genetics and demonstrates how traits are inherited independently.
How to Use This Calculator
Select the genotype for each parent's two traits from the dropdown menus. For Trait 1, choose AA (homozygous dominant), Aa (heterozygous), or aa (homozygous recessive). For Trait 2, choose BB, Bb, or bb. Both parents default to AaBb, the classic dihybrid cross. Click Calculate to generate the Punnett square, view genotype and phenotype distributions, and explore interactive charts.
Applications in Genetics
Dihybrid crosses are essential for understanding inheritance patterns in genetics research, plant and animal breeding, and pedigree analysis. They help predict the likelihood of specific trait combinations in offspring, such as seed shape and color in pea plants (Mendel's original experiments), coat color and pattern in animals, or the inheritance of two genetic conditions in humans.
Frequently Asked Questions
What is a dihybrid cross Punnett square?
A dihybrid cross Punnett square is a 4x4 grid used in genetics to predict the probability of offspring inheriting two different traits, each controlled by two alleles (A/a and B/b). It shows all 16 possible genotype combinations from crossing two parents and is used to determine genotypic and phenotypic ratios.
What is the phenotypic ratio of a dihybrid cross?
For a classic dihybrid cross between two heterozygous parents (AaBb x AaBb), the phenotypic ratio is 9:3:3:1. This means 9/16 offspring show both dominant traits, 3/16 show dominant trait 1 with recessive trait 2, 3/16 show recessive trait 1 with dominant trait 2, and 1/16 show both recessive traits.
How do you calculate a dihybrid cross Punnett square?
To calculate a dihybrid cross Punnett square, first determine each parent's possible gamete combinations using the FOIL method. For a parent with genotype AaBb, the gametes are AB, Ab, aB, and ab. Then create a 4x4 grid with the mother's gametes across the top and father's gametes down the left side. Fill each cell by combining the alleles from each parent, resulting in 16 possible offspring genotypes.
What are the 9 possible genotypes in a dihybrid cross?
The 9 possible genotypes in a dihybrid cross are: AABB, AABb, AAbb, AaBB, AaBb, Aabb, aaBB, aaBb, and aabb. These represent all possible combinations of dominant and recessive alleles for two traits, following Mendelian inheritance patterns.
Is the dihybrid cross Punnett square calculator free?
Yes, the dihybrid cross Punnett square calculator is completely free to use with no registration or account required. You can calculate unlimited dihybrid crosses and share results via URL.
What is the genotypic ratio in a dihybrid cross?
For a heterozygous dihybrid cross (AaBb x AaBb), the genotypic ratio is 1:2:1:2:4:2:1:2:1. This corresponds to the 9 possible genotypes: 1 AABB, 2 AABb, 1 AAbb, 2 AaBB, 4 AaBb, 2 Aabb, 1 aaBB, 2 aaBb, and 1 aabb. The ratio is derived from the 16-cell Punnett square.
How is a dihybrid cross different from a monohybrid cross?
A monohybrid cross tracks inheritance of one trait (using a 2x2 Punnett square with 4 offspring combinations), while a dihybrid cross tracks two traits simultaneously (using a 4x4 Punnett square with 16 combinations). Dihybrid crosses demonstrate Mendel's law of independent assortment, showing that alleles for different traits segregate independently during gamete formation.
What does AaBb mean in genetics?
AaBb represents a dihybrid genotype where the individual is heterozygous for both traits. The 'A' and 'a' represent the two alleles for the first trait (with A being dominant), while 'B' and 'b' represent the two alleles for the second trait (with B being dominant). A heterozygous individual produces four types of gametes: AB, Ab, aB, and ab.