Class 12 Botany simulations · Principles of Inheritance and Variation

Incomplete dominance and co-dominance

Cross snapdragons (incomplete dominance) or combine ABO alleles (co-dominance) and compare the offspring.

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What to notice

In incomplete dominance the F₂ phenotypic ratio equals the genotypic ratio, 1 : 2 : 1.

Key relation

Snapdragon: RR (red) × rr (white) → Rr (pink) ; ABO: Iᴬ Iᴮ → group AB

Try this

Self the pink F₁ (Rr × Rr). What fraction of flowers are pink?

What you can change

• Example: choose Snapdragon flower colour, ABO blood group
• Parent 1: choose RR / IᴬIᴬ, Rr / IᴬIᴮ, rr / ii
• Parent 2: choose RR / IᴮIᴮ, Rr / IᴬIᴮ, rr / ii

More in Principles of Inheritance and Variation

• Dihybrid cross: independent assortment
• Mendel’s monohybrid cross
• Sex determination and X-linked traits

See all Class 12 Botany simulations or every Physica simulation.