Trihybrid Cross Calculator

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A_ B_ C_ (all dominant traits)Classic trihybrid ratio
42.19% (27/64 cells)

Probability that offspring expresses dominant phenotype at all three loci

A_ B_ cc14.06% (9/64 cells)
A_ bb C_14.06% (9/64 cells)
aa B_ C_14.06% (9/64 cells)
A_ bb cc4.69% (3/64 cells)
aa B_ cc4.69% (3/64 cells)
aa bb C_4.69% (3/64 cells)
aa bb cc (all recessive)1.56% (1/64 cells)
Parent 1 gamete types8 gamete types
Parent 2 gamete types8 gamete types
Punnett square cells64 cells (8 x 8)
Phenotype ratio27:9:9:9:3:3:3:1
P(dominant at A)0.75
P(dominant at B)0.75
P(dominant at C)0.75
P(dominant at A)0.75
P(dominant at B)0.75
P(dominant at C)0.75

Trihybrid cross: AaBbCc x AaBbCc (both parents triply heterozygous)

  • Parent 1 produces 8 gamete types and Parent 2 produces 8 gamete types, giving 64 cells (8 x 8) in the Punnett square.
  • The classic 27:9:9:9:3:3:3:1 phenotype ratio means 27/64 offspring show all three dominant traits, and only 1/64 shows all three recessive traits.
  • This calculation assumes complete dominance at each locus and independent assortment (genes on different chromosomes or far apart on the same one).

Next stepFor genes that show incomplete dominance, codominance, or linkage, the product rule for independent loci no longer applies and a full molecular approach is needed.

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