Punnett square calculator (genetic cross)
Build the Punnett square for a monohybrid, dihybrid or trihybrid cross, such as Aa × Aa or AaBb × AaBb, and see the genotype and phenotype ratios of the offspring.
How to useGenetic cross and Punnett square
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Punnett square calculator (genetic cross): what it is for
Type the genotypes of both parents, such as Aa × Aa or AaBb × AaBb, and the tool builds the Punnett square with every gamete, counts the combinations and shows the fractions and percentages of each genotype and phenotype, plus the simplified phenotypic ratio, such as 3:1 or 9:3:3:1. It assumes complete dominance and independent assortment, as in Mendel's laws.
The calculations run in your browser; nothing you type is sent to any server.
How to use
- Type the genotype of each parent.
- See the Punnett square.
- Check the genotype and phenotype ratios.
When to use it
- Solving genetics homework.
- Studying Mendel's laws.
- Preparing biology lessons.
Frequently asked questions
How do I type the genotypes?
Use a pair of letters for each gene, uppercase for the dominant allele and lowercase for the recessive one: Aa, AABb, AaBbCc. Both parents must have the same genes, in the same order.
What is a Punnett square?
It is a table that crosses every possible gamete of one parent with every gamete of the other. Each cell is a possible offspring, and all of them are equally likely, according to Mendel's first and second laws.
Why does a dihybrid cross give 9:3:3:1?
In the cross AaBb × AaBb, each gene segregates independently. Each one gives 3/4 dominant and 1/4 recessive, and combining the two gives 9/16 with both dominant traits, 3/16 and 3/16 with one of each, and 1/16 with both recessive traits. The tool assumes complete dominance and genes on different chromosomes.
Is it really free?
Yes, 100% free. No sign-up, no subscription and no usage limits. All Tools123 tools are free and run right in your browser.