1. What is a Dihybrid Cross?

A dihybrid cross examines the inheritance of two different traits simultaneously. It demonstrates Mendel's principle of independent assortment, where alleles for different traits are distributed independently of one another during gamete formation.

2. Understanding the 9:3:3:1 Ratio

The classic 9:3:3:1 phenotypic ratio appears in the offspring of heterozygous parents (AaBb × AaBb):

Where:

• A_B_ — Dominant for both traits
• A_bb — Dominant for first trait, recessive for second
• aaB_ — Recessive for first trait, dominant for second
• aabb — Recessive for both traits

3. How the Calculator Works

Process: The calculator generates all possible gametes for each parent, creates a Punnett square of their combinations, then determines the phenotypic ratio of the offspring.

4. Using the Calculator

Instructions: Select the genotype for each parent and trait. The calculator will show the Punnett square and phenotypic ratio of possible offspring.

5. Frequently Asked Questions (FAQ)

Q1: When does the 9:3:3:1 ratio appear?
A: Only when both parents are heterozygous for both traits (AaBb × AaBb) and the genes are on different chromosomes or far apart on the same chromosome.

Q2: What if the ratio differs from 9:3:3:1?
A: Different ratios suggest gene linkage (genes close together on same chromosome) or other genetic interactions.

Q3: How many boxes are in a dihybrid Punnett square?
A: 16 boxes (4 gametes from each parent × 4 gametes from the other parent).

Q4: Can this calculator handle incomplete dominance?
A: No, this calculator assumes complete dominance/recessiveness for both traits.

Q5: What's the difference between genotype and phenotype ratio?
A: Genotype ratio shows genetic combinations (e.g., AABB, AABb), while phenotype ratio shows observable traits (e.g., A_B_).