1. What is Phenotypic Ratio?

The phenotypic ratio is the relative number of offspring manifesting particular traits in a genetic cross. In a dihybrid cross (two traits), the classic ratio is 9:3:3:1 when both parents are heterozygous for both traits.

2. How Does the Calculator Work?

The calculator determines the expected phenotypic ratio based on Mendelian inheritance:

Key Ratios:

• Heterozygous × Heterozygous: 3:1 (single trait)
• Heterozygous × Homozygous Dominant: 1:0 (all dominant phenotype)
• Heterozygous × Homozygous Recessive: 1:1 (test cross ratio)

3. Importance of Phenotypic Ratios

Details: Phenotypic ratios help predict offspring traits, understand inheritance patterns, and verify genetic hypotheses through chi-square tests.

4. Using the Calculator

Tips: Select the genotype for each trait. For a classic dihybrid cross, choose "Heterozygous" for both traits.

5. Frequently Asked Questions (FAQ)

Q1: Why is the ratio 9:3:3:1 for dihybrid crosses?
A: This represents all combinations of two 3:1 ratios (9 dominant for both, 3 dominant for A/recessive for B, 3 recessive for A/dominant for B, 1 recessive for both).

Q2: What if the observed ratio differs from expected?
A: This may indicate genetic linkage, incomplete dominance, or other non-Mendelian inheritance patterns.

Q3: How does independent assortment affect the ratio?
A: Independent assortment of genes on different chromosomes produces the 9:3:3:1 ratio in dihybrid crosses.

Q4: Can this calculator handle more than two traits?
A: No, this calculator is specifically for dihybrid (two-trait) crosses.

Q5: What about codominance or incomplete dominance?
A: These patterns produce different ratios and would require a modified calculator.