Step 2: Set up the cross using the genotypes determined for each parent.

1. Steps to execute a dihybrid crossStep 1: Determine the genotypes of the parents given the following information: A male who is heterozygous for widow’s peak and brown hair has an offspring with a female who is heterozygous for widow’s peak and brown hair.Genotypes:Father- WwBb Mother- WwBb

2. Step 2: Set up the cross using the genotypes determined for each parent. • WwBb x WwBb

3. Step 3: Set up the Punnett square using the genotypes of each parent. WwBb x WwBb Remember that the genes for each trait consist of two alleles. The alleles for each trait must be separated from each other when the Punnett square is set up. WB Wb wB wb WB Wb wB wb

4. Possible allelic combinations of sperm WBWbwBwb Possible allelic combinations of egg WB Wb wB wb

5. Step 4: Determine the genotypic ratios WBWbwBwb WB Wb wB wb

7. Genotypic ratios • WWBB= 1/16 • WWBb= 2/16 • WWbb= 1/16 • WwBB= 2/16 • WwBb= 4/16 • Wwbb= 2/16 • wwBB=1/16 • wwBb= 2/16 • wwbb= 1/16 • 1:2:1:2:4:2:1:2:1

8. Step 5:Determine the phenotypic ratios WBWbwBwb WB Wb wB wb

9. Phenotypic Ratios • Widow’s peak and Brown hair= 9/16 • Widow’s peak and blonde hair= 3/16 • No widow’s peak and brown hair= 3/16 • No widow’s peak and blonde hair= 1/16 • 9:3:3:1

10. WBWbwBwb WB Wb wB wb