Probability of Inheritance Calculator

Genetics uses letter-based codes to predict which traits — like eye color or height — offspring are likely to inherit from their parents. Enter your Parent 1 and Parent 2 genotypes, select a cross type (monohybrid for 1 trait or dihybrid for 2), and specify the dominant alleles to get the probability of dominant and recessive phenotypes. Secondary outputs include the likelihood of heterozygous, homozygous dominant, and homozygous recessive genotypes, with optional genotypic and phenotypic ratios.

Enter genotype using capital letters for dominant alleles

Enter genotype using lowercase letters for recessive alleles

Specify which alleles are dominant

Results

Probability of Dominant Phenotype

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Probability of Recessive Phenotype

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Probability of Heterozygous Genotype

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Probability of Homozygous Dominant

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Probability of Homozygous Recessive

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Results Table

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Frequently Asked Questions

What is a Punnett square and how does it work?

A Punnett square is a genetic diagram that predicts the probability of offspring inheriting specific traits from their parents. It shows all possible genetic combinations by crossing the gametes from each parent, helping visualize genotype and phenotype ratios.

How do I read genotype notation like 'Aa' or 'AaBb'?

Capital letters represent dominant alleles, while lowercase letters represent recessive alleles. 'Aa' means heterozygous for one trait, 'AA' is homozygous dominant, 'aa' is homozygous recessive, and 'AaBb' represents genotypes for two different traits.

What's the difference between genotype and phenotype?

Genotype refers to the genetic makeup (the actual alleles present), while phenotype is the observable physical characteristic. For example, 'Aa' is a genotype, while 'brown eyes' is the corresponding phenotype if A represents the brown eye allele.

How accurate are genetic inheritance predictions?

Punnett squares provide theoretical probabilities based on Mendelian genetics. While very useful for simple traits, real inheritance can be more complex due to factors like incomplete dominance, codominance, and polygenic traits affecting the actual outcomes.

Can I use this calculator for multiple traits at once?

Yes, the calculator supports dihybrid crosses for two traits simultaneously. For example, you can analyze both eye color and hair texture inheritance patterns in a single calculation, though this creates more complex probability combinations.

What does it mean if a trait is dominant or recessive?

A dominant trait only needs one copy of the allele to be expressed in the phenotype, while a recessive trait requires two copies (one from each parent) to be visible. Dominant alleles are typically represented by capital letters.

How do I interpret the probability percentages?

The percentages show the likelihood of each outcome occurring in offspring. For example, 75% dominant phenotype means that if the parents had many offspring, approximately 3 out of every 4 would show the dominant trait.