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

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?

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 ____________________________

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

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

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

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

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