Monohybrid cross Punnett square (3:1)
The classic single-gene Punnett square — two heterozygous parents (Bb × Bb) crossed for eye colour. The engine computes the gametes, the 2×2 grid, and the canonical 3:1 dominant-to-recessive phenotype ratio with a 1:2:1 genotype ratio.
For the biology teacher or student learning Mendelian inheritance
What this shows
The monohybrid cross is where every genetics course starts: one gene, two heterozygous parents. Here both parents are Bb for eye colour — B (brown) is dominant, b (blue) recessive. You write only the cross; the engine does the Mendelian bookkeeping.
Each Bb parent makes two gametes, B and b, so the grid is 2×2. The engine fills it — BB, Bb, Bb, bb — and computes the two ratios every student memorises: a 3:1 phenotype ratio (3 brown-eyed : 1 blue-eyed) and a 1:2:1 genotype ratio (1 BB : 2 Bb : 1 bb). The single recessive bb box is tinted apart from the three dominant boxes, and the trait line names the phenotypes so the legend reads in plain English. Allele case sets dominance — uppercase is dominant — so the notation is exactly what a textbook uses.