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)

http://www.dnaftb.org/dnaftb/5/concept/index.html

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

YyRr

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