Punnett Square Calculator

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A monohybrid cross tracks one gene; a dihybrid cross tracks two independently assorting genes simultaneously.
Complete dominance: dominant allele fully masks recessive. Incomplete: heterozygotes show blended phenotype. Codominance: both alleles expressed equally. X-linked: gene is on the X chromosome.
Give the dominant trait a name so the insight panel uses it instead of "dominant".
Give the recessive trait a name so the insight panel uses it instead of "recessive".
Genotype ratio (AA : Aa : aa)Classic 3:1 ratio
1 : 2 : 1
Dominant phenotype75%
Recessive phenotype25%
Heterozygous carriers (Aa)50%
Homozygous recessive (aa)25%
Phenotype ratio3 : 1

Genotype ratio 1 : 2 : 1 under complete dominance.

  • 75% of offspring are expected to show the dominant phenotype; 25% the recessive phenotype.
  • 50% are heterozygous carriers (Aa): they show the dominant trait but can pass the recessive allele to their own offspring.
  • These ratios are probabilities over many offspring. Any individual offspring has its own independent probability, regardless of what siblings inherit.

Next stepSwitch to Dihybrid mode to model two independently assorting genes at once and see the 9:3:3:1 phenotype split.

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