Type the two parent genotypes and read off both ratios at once: the genotypic ratio, which counts each allele combination, and the phenotypic ratio, which counts what the offspring look like. The page opens on a trihybrid cross, AaBbCc × AaBbCc, whose 64-cell square resolves to the 27:9:9:9:3:3:3:1 phenotypic ratio; any cross from one to five genes works the same way.
The two ratios describe the same square at different levels. A genotypic ratio lists every distinct genotype and how often it occurs: for Aa × Aa that is 1 AA : 2 Aa : 1 aa. A phenotypic ratio merges the genotypes that look alike; with A dominant, AA and Aa share a phenotype, so 1:2:1 becomes 3:1. Under incomplete dominance or codominance the heterozygote is visible, and the two ratios coincide. The Analysis panel prints both, in textbook order, and flags the classic ones such as 9:3:3:1 or 1:1:1:1 by name.
You can predict any ratio without a grid by treating each gene separately and multiplying. Each heterozygous pair in AaBbCc × AaBbCc gives 3 dominant : 1 recessive, so the eight phenotypes are the terms of (3:1)³: 3 × 3 × 3 = 27 for dominant at all three genes, 3 × 3 × 1 = 9 for each combination with one recessive trait, 3 for two recessive traits and 1 for aabbcc. The same multiplication gives probabilities: the chance of an offspring that is AaBbCc is 1/2 × 1/2 × 1/2 = 1/8, and the chance of aabbcc is 1/64. Genes that are homozygous in a parent simply drop out; AABbCc × AaBbcc has only two segregating genes and a 3:1 × 1:1 pattern, which the calculator reports as 3:3:1:1.
AaBbCc for an exact genotype, A_B_cc for dominant at the first two genes and recessive at the third, or __bb__ for any offspring that is bb.Four heterozygous genes give 256 cells, 81 genotypes and 16 phenotypes in an 81:27:27:27:27:9:9:9:9:9:9:3:3:3:3:1 ratio; five give 1,024 cells and 243 genotypes. The square becomes hard to read at that size, but the ratios stay exact because the calculator counts cells rather than drawing estimates. Zoom into the square with ctrl and the mouse wheel or a pinch to inspect individual cells. For two-gene crosses with the full square in view, start from the dihybrid cross calculator; for a single gene, the monohybrid cross page.
Enter both parents' genotypes; the calculator counts every cell of the Punnett square, groups identical genotypes for the genotypic ratio and identical appearances for the phenotypic ratio, then simplifies both. For Aa × Aa that is 1:2:1 and 3:1.
1:2:1:2:4:2:1:2:1, nine genotypes across sixteen cells. AaBb is the most common at 4/16; the four double homozygotes (AABB, AAbb, aaBB, aabb) are 1/16 each.
27:9:9:9:3:3:3:1 for AaBbCc × AaBbCc: eight phenotypes across 64 cells, with 27/64 dominant for all three traits and 1/64 recessive for all three.
Yes, with the product rule. Work out each gene's ratio separately (3:1 for Aa × Aa, 1:1 for Aa × aa, all dominant for AA × Aa) and multiply them. The calculator does the same in the background and shows the result immediately.
27 when both parents are heterozygous for all three (3 × 3 × 3), and in general 3ⁿ for n heterozygous genes. Four genes give 81 genotypes and five give 243.