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# Step 2: Set up the cross using the genotypes determined for each parent. - PowerPoint PPT Presentation

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## PowerPoint Slideshow about ' Step 2: Set up the cross using the genotypes determined for each parent.' - hector-andrews

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Presentation Transcript

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

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

• WwBb x WwBb

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

WBWbwBwb

Possible allelic combinations of egg

WB

Wb

wB

wb

Step 4: Determine the genotypic ratios

WBWbwBwb

WB

Wb

wB

wb

• 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

Step 5:Determine the phenotypic ratios

WBWbwBwb

WB

Wb

wB

wb

• 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

WBWbwBwb

WB

Wb

wB

wb