Punnett Square Inheritance Calculator
Calculate the probability of offspring genotypes and phenotypes for monohybrid or dihybrid crosses using Punnett square analysis.
Formula & Method
Monohybrid Cross: Each parent contributes one allele per gene. A 2×2 Punnett square yields 4 possible offspring combinations. Probabilities are calculated as the fraction of each genotype out of 4 total boxes.
Dihybrid Cross: Each parent contributes one allele per gene for two independent genes. A 4×4 Punnett square yields 16 possible offspring combinations. Probabilities are calculated as the fraction of each genotype/phenotype out of 16 total boxes.
Genotype Probability: P(genotype) = count of that genotype in square ÷ total boxes
Phenotype Probability: Dominant phenotype = any genotype with at least one dominant allele (e.g., AA or Aa). Recessive phenotype = homozygous recessive only (aa).
Genotypic Ratio (Monohybrid Aa × Aa): 1 AA : 2 Aa : 1 aa
Phenotypic Ratio (Monohybrid Aa × Aa): 3 Dominant : 1 Recessive
Phenotypic Ratio (Dihybrid AaBb × AaBb): 9 A_B_ : 3 A_bb : 3 aaB_ : 1 aabb
Assumptions & References
- Assumes simple Mendelian inheritance (complete dominance).
- Assumes independent assortment of alleles (Mendel's Second Law).
- Does not account for linked genes, incomplete dominance, codominance, or epistasis.
- Uppercase letters represent dominant alleles; lowercase represent recessive alleles.
- Both alleles in a genotype must use the same letter (e.g., Aa, not Ab).
- For dihybrid crosses, Gene A and Gene B must use different letters.
- Reference: Mendel, G. (1866). Versuche über Pflanzenhybriden. Verhandlungen des naturforschenden Vereines in Brünn.
- Reference: Griffiths, A.J.F. et al. Introduction to Genetic Analysis, 12th ed. W.H. Freeman.