Monohybrid Cross Calculator
Predict offspring probabilities for a single Mendelian trait. Customize allele symbols and phenotype descriptions to generate a custom 2x2 Punnett square.
Trait Details & Parental Genotypes
Customize dominant and recessive phenotypes, then select parent genotypes.
Mendelian 2×2 Grid
| A | a | |
|---|---|---|
| A | AA | Aa |
| a | Aa | aa |
Trait Probabilities
Genotype Ratio
Phenotype Ratio
Dominance Principle
In complete Mendelian dominance, heterozygous individuals (Aa) display the dominant phenotype. Thus, a cross between two heterozygotes yields a 3:1 phenotypic ratio.
Monohybrid Cross Parental Combinations Table
| Parental Genotype Combination | Offspring Genotypes | Dominant Phenotype % | Recessive Phenotype % |
|---|---|---|---|
| AA × AA (Homozygous Dom × Dom) | 100% AA | 100% | 0% |
| AA × aa (Purebred Cross) | 100% Aa | 100% | 0% |
| Aa × Aa (Monohybrid Hybrid Cross) | 25% AA, 50% Aa, 25% aa | 75% | 25% |
| Aa × aa (Test Cross) | 50% Aa, 50% aa | 50% | 50% |
| aa × aa (Homozygous Rec × Rec) | 100% aa | 0% | 100% |
Calculation Methodology & Biological Principles
Mendelian Segregation
During meiosis, homologous chromosomes separate, segregating allele pairs into separate haploid gametes with equal probability (50% each).
Classic Ratios
Aa × Aa Cross:
- Genotypic ratio: 1 AA : 2 Aa : 1 aa (1:2:1)
- Phenotypic ratio: 3 Dominant : 1 Recessive (3:1)
Frequently Asked Questions
What is a Monohybrid Cross? ▼
A monohybrid cross is a genetic cross between two individuals that involves the study of a single trait governed by a single gene locus.
What is Mendel's Law of Segregation? ▼
Mendel's First Law states that paired alleles separate (segregate) during meiosis into individual gametes, so each gamete receives only one allele for each gene.
What are the expected ratios of a monohybrid cross between two heterozygotes (Aa × Aa)? ▼
Crossing two heterozygous parents yields a 1:2:1 genotypic ratio (25% AA, 50% Aa, 25% aa) and a 3:1 phenotypic ratio (75% dominant phenotype, 25% recessive phenotype).
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