Steps to execute a dihybrid cross
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Step 2: Set up the cross using the genotypes determined for each parent. PowerPoint PPT Presentation


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

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Step 2 set up the cross using the genotypes determined for each parent

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

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

  • WwBb x WwBb


Step 2 set up the cross using the genotypes determined for each parent

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 WbwB wb

WB

Wb

wB

wb


Step 2 set up the cross using the genotypes determined for each parent

Possible allelic combinations of sperm

WBWbwBwb

Possible allelic combinations of egg

WB

Wb

wB

wb


Step 2 set up the cross using the genotypes determined for each parent

Step 4: Determine the genotypic ratios

WBWbwBwb

WB

Wb

wB

wb


Genotypic ratios

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


Step 2 set up the cross using the genotypes determined for each parent

Step 5:Determine the phenotypic ratios

WBWbwBwb

WB

Wb

wB

wb


Phenotypic ratios

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


Step 2 set up the cross using the genotypes determined for each parent

WBWbwBwb

WB

Wb

wB

wb


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