1. Or Crossing two traits at a time
Di=Two!
Dihybrid Crosses
Or Crossing two traits at a time

2. Crossing Two Traits at a Time
A man who is Heterozygous for Brown eyes(B) and Straight Hair(H) has children with a woman who is homozygous recessive for blue eyes(b) and curly hair(h).
What percentage of their offspring would be heterozygous for both traits?

3. STEP 1- Find your parents
A man who is Heterozygous for Brown eyes(B) and Straight Hair(H) has children with a woman who is homozygous recessive for blue eyes(b) and curly hair(h).
____________________________ X ____________________________

4. Step 2- Set Up a Punnet Square for each trait
BbHh X bbhh

5. Step 3- Multiply to find your answer
What percent of their offspring will be heterozygous for both traits?
BbHh X bbhh B b Bb bb H h Hh hh
Fraction of Heterozygous Brown Eyes
Fraction of Heterozygous Straight Hair
Fraction of Heterozygous for Both

6. Fraction of Brown eyes and Curly Hair
How About Phenotypes?
What percent of their offspring will have Brown eyes AND curly hair?
BbHh X BbHh B b BB Bb bb H h HH Hh hh
Fraction of Brown Eyes
Fraction of Curly Hair
Fraction of Brown eyes and Curly Hair

7. Practice Problem 1 BBhh X BbHh
What percent of their offspring will be heterozygous for Brown eyes and homozygous recessive for curly hair?
BBhh X BbHh

8. Practice Problem 2 bbhh X BbHh
What percent of their offspring will have the genotype bbhh?
bbhh X BbHh