Genotype Ratio Calculator

Calculate genotype and phenotype ratios for different inheritance patterns including complete dominance, incomplete dominance, codominance, and sex-linked traits.

Inheritance Pattern

Parent 1 Genotype

Parent 2 Genotype

Phenotype Labels

Dominant Phenotype

Recessive Phenotype

Genotype Ratios

Phenotype Ratios

Classic Ratio Format

Genotypic Ratio:

Phenotypic Ratio:

Offspring Distribution

Probability Breakdown

Genotype	Phenotype	Probability	Expected (per 100)

Interpretation

Understanding Inheritance Patterns

Different traits are inherited through various patterns beyond simple Mendelian genetics. Understanding these patterns helps predict offspring traits and explains the diversity we observe in nature.

Complete Dominance (Mendelian)

The classic pattern discovered by Gregor Mendel. One allele (dominant) completely masks the expression of another (recessive). Heterozygotes (Aa) show the same phenotype as homozygous dominant (AA) individuals.

Example: Pea plant flower color - Purple (P) is dominant over white (p)

Genotypic ratio (Aa × Aa): 1 AA : 2 Aa : 1 aa

Phenotypic ratio (Aa × Aa): 3 Purple : 1 white

Incomplete Dominance

Neither allele is completely dominant. Heterozygotes display a blended or intermediate phenotype between the two homozygous forms. The genotypic and phenotypic ratios are the same.

Example: Snapdragon flower color - Red (R^R) × White (R'R') = Pink (RR')

Cross RR' × RR': 1 Red : 2 Pink : 1 White

Note: All three genotypes have different phenotypes

Codominance

Both alleles are fully expressed simultaneously in heterozygotes. Unlike incomplete dominance, there's no blending - both traits appear together. Common in blood types and coat color patterns.

Example: Human ABO blood types - I^A and I^B are codominant

I^A I^B genotype: Type AB blood (both A and B antigens present)

Roan cattle: Red and white hair appear together, not blended

Sex-Linked Inheritance (X-linked)

Genes located on sex chromosomes (usually X chromosome) show unique inheritance patterns. Males (XY) are hemizygous - they only have one X chromosome, so they express whatever allele is present. Females (XX) need two recessive alleles to show recessive trait.

Examples: Color blindness, hemophilia, Duchenne muscular dystrophy

Pattern: More common in males; carrier females don't show trait

Carrier mother × Normal father: 50% sons affected, 50% daughters carriers

Comparing Inheritance Patterns

Pattern	Heterozygote Phenotype	Typical Ratio (Aa × Aa)	Example
Complete Dominance	Same as dominant homozygote	3:1 (phenotype)	Pea plant height
Incomplete Dominance	Intermediate/blended	1:2:1 (same for both)	Snapdragon color
Codominance	Both alleles expressed	1:2:1 (same for both)	ABO blood type
Sex-Linked	Depends on sex	Varies by parent genotypes	Color blindness

Real-World Examples

ABO Blood Type (Codominance + Multiple Alleles)

Three alleles (I^A, I^B, i). I^A and I^B are codominant; both are dominant over i.

• I^A I^A or I^A i = Type A
• I^B I^B or I^B i = Type B
• I^A I^B = Type AB (codominance)
• ii = Type O

Sickle Cell Anemia (Incomplete Dominance)

Shows incomplete dominance at the molecular level.

• HbA HbA = Normal (all normal hemoglobin)
• HbA HbS = Sickle cell trait (some sickled cells)
• HbS HbS = Sickle cell disease (mostly sickled cells)

Hemophilia (X-linked Recessive)

Blood clotting disorder; mostly affects males.

• X^H X^H = Normal female
• X^H X^h = Carrier female (normal)
• X^h X^h = Affected female (rare)
• X^H Y = Normal male
• X^h Y = Affected male

Snapdragon Flowers (Incomplete Dominance)

Classic example of incomplete dominance in plants.

• R^R R^R = Red flowers
• R^R R^W = Pink flowers (blend)
• R^W R^W = White flowers
• Cross pink × pink = 1:2:1 ratio

Common Genotypic and Phenotypic Ratios

Monohybrid Cross (Aa × Aa)

• Genotypic: 1 AA : 2 Aa : 1 aa
• Phenotypic (Complete Dominance): 3 Dominant : 1 Recessive
• Phenotypic (Incomplete/Codominance): 1 : 2 : 1

Test Cross (Aa × aa)

• Genotypic: 1 Aa : 1 aa (or 50% : 50%)
• Phenotypic (Complete Dominance): 1 Dominant : 1 Recessive
• Used to determine if dominant phenotype is AA or Aa

Sex-Linked (X^A X^a × X^A Y)

• Daughters: 50% X^A X^A (normal), 50% X^A X^a (carrier)
• Sons: 50% X^A Y (normal), 50% X^a Y (affected)
• Males more likely to show recessive sex-linked traits

References

The inheritance patterns and genetics concepts are based on established scientific literature:

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Punnett Square Calculator Phenotype Probability Calculator Allele Frequency Calculator Hardy-Weinberg Equilibrium Calculator Selection Coefficient Calculator

Educational Disclaimer: This genotype ratio calculator is designed for educational purposes to demonstrate various inheritance patterns. Real genetic inheritance can be more complex, involving multiple genes (polygenic traits), environmental factors, epigenetic modifications, and gene interactions (epistasis). Sex-linked traits shown here focus on X-linked inheritance; Y-linked and mitochondrial inheritance follow different patterns. For genetic counseling or medical genetics questions, consult qualified genetics professionals.