Codominance Calculator

In codominance, both inherited alleles are expressed equally in offspring — like how a person with blood type AB displays both A and B traits simultaneously. Enter the first and second alleles for Parent 1 and Parent 2 into the Codominance Calculator, along with an optional trait name, to generate a Punnett square analysis. You'll see the most common phenotype percentage, total genotype combinations, heterozygous offspring percentage, and codominant expression rate.

Enter first allele for Parent 1

Enter second allele for Parent 1

Enter first allele for Parent 2

Enter second allele for Parent 2

Optional name for the trait being analyzed

Display ratios for each genotype

Show phenotype predictions

Results

Most Common Phenotype

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Total Genotype Combinations

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Heterozygous Offspring

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Codominant Expression

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Results Table

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Frequently Asked Questions

What is codominance in genetics?

Codominance occurs when both alleles in a heterozygote are fully expressed simultaneously, without blending. A classic example is ABO blood types, where IA and IB alleles are codominant, resulting in AB blood type.

How is codominance different from incomplete dominance?

In codominance, both traits are fully expressed together (like AB blood type), while in incomplete dominance, the traits blend to create an intermediate phenotype (like pink flowers from red and white parents).

Can I use this calculator for human traits?

Yes, this calculator works for any codominant traits including human examples like ABO blood types, HLA antigens, and certain protein variants. Just enter the appropriate allele symbols.

What do the genotype ratios tell me?

Genotype ratios show the probability of each genetic combination occurring in offspring. For example, a 1:2:1 ratio means 25% chance of each homozygote and 50% chance of the heterozygote.

How do I interpret codominant phenotypes?

In codominance, heterozygotes express both parental traits simultaneously. The calculator shows which offspring will display single traits versus combined codominant expression.

What allele notation should I use?

Use standard genetic notation like IA, IB for blood types, or any letter/symbol system. The calculator treats different symbols as different alleles and analyzes their inheritance patterns.

Can this calculator handle multiple alleles?

This calculator works with any pair of alleles for each parent. For traits with more than two allele variants in a population, run separate calculations for different parental combinations.