Trihybrid Cross Calculator
Predict the genotypic and phenotypic ratios of offspring for crosses involving three independent genes.
Parental Genotypes
Select genotypes for Mother and Father across Gene 1 (A/a), Gene 2 (B/b), and Gene 3 (C/c).
Parent 1 (Mother)
Parent 2 (Father)
Genotypic Breakdown (All 27 Combinations)
Trihybrid Ratios
Phenotypic Probabilities (Simple Dominance)
Expert Tip
When crossing two triple heterozygotes (AaBbCc × AaBbCc), the phenotypic ratio for the three traits is 27:9:9:9:3:3:3:1.
Methodology & Equations
Product Rule of Probability
Instead of making an 8×8 grid (64 cells), we calculate the probability of each gene pair independently and multiply them together. For example:
P(AaBbCc) = P(Aa) × P(Bb) × P(Cc)
The 8 Phenotypic Classes
Assuming complete dominance, three genes yield 23 = 8 unique phenotype categories:
- **A_B_C_** (Dominant for all three traits, expected 27/64)
- **A_B_cc**, **A_bbC_**, **aaB_C_** (Dominant for two traits, expected 9/64 each)
- **A_bbcc**, **aaB_cc**, **aabbC_** (Dominant for one trait, expected 3/64 each)
- **aabbcc** (Recessive for all three, expected 1/64)
How to Calculate a Trihybrid Cross: Step-by-Step
Below is a step-by-step example calculating the probability of getting an AaBBCc offspring from a cross between two AaBbCc parents:
Analyze Gene 1 (A)
Cross the A alleles of both parents (Aa × Aa). The probability of getting heterozygous Aa is 1/2 (50%).
Analyze Gene 2 (B)
Cross the B alleles of both parents (Bb × Bb). The probability of getting homozygous dominant BB is 1/4 (25%).
Analyze Gene 3 (C) & Multiply
Cross the C alleles of both parents (Cc × Cc). The probability of getting Cc is 1/2 (50%).
Multiply the probabilities: 1/2 (Aa) × 1/4 (BB) × 1/2 (Cc) = 1/16 (6.25%).
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Dihybrid Cross Calculator
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Generate 2x2 Punnett squares and calculate genotypic probabilities.