Dihybrid Crosses


Two Characters- Two Traits for each


The place to learn this best: DNA Learning Center Part 5: Genetic Inheritance follows Rules

Do the problem (dihybrid crosses)




Character: Seed color

Traits: • Yellow (dominant)

              • Green (recessive)


Character: Seed coat

Traits: • Round (dominant)

              • Wrinkled (recessive)


If you have two characters? How does this work? (See figure 14.7, page 245)








Parental: Yellow, Round (pure) x Green, Wrinkled (pure)

                                    YYRR        x        yyrr


F1: Yellow, Green



Gametes: 4 possible gamets from each parent. YR, Yr, yR, yr

Why? Because they independently assort! Mendel’s 2nd Law.


When you cross two hybrid individuals this is called a Dihybrid Cross: YyRr x YyRr


F2: Big Punnett Square (16 squares)


Phenotype ratio: 9:3:3:1