Dihybrid Crosses

• What do monohybrid crosses examine?

  Alleles of one gene across generations
• What do dihybrid crosses examine?

  Alleles of two genes across generations

  
• How can dihybrid crosses be used in genetics?

  To show inheritance of two different characteristics

  
• How do the genetic diagrams for monohybrid and dihybrid crosses compare?

  They are very similar in structure
• What is a key difference in the number of genotypes and phenotypes in dihybrid crosses compared to monohybrid crosses?

  More genotypes and phenotypes are involved

  
• How should alleles be written for dihybrid crosses?

  Two alleles for one gene followed by two for another
• What are the alleles for the coat color gene in horses?

  B (black) and b (chestnut)

  
• What are the alleles for the eye color gene in horses?

  E (brown) and e (blue)
• Why are the genes for coat color and eye color in horses considered unlinked?

  They are located on different non-homologous chromosomes
• What is the genotype of a horse that is heterozygous for both genes?

  BbEe
• What is the genotype of a horse that is homozygous for one gene and heterozygous for the other?

  bbEe
• What is the predicted ratio of phenotypes in the offspring?

  • 3 black coat, brown eyes
  • 3 chestnut coat, brown eyes
  • 1 black coat, blue eyes
  • 1 chestnut coat, blue eyes

  
• What is the predicted ratio of genotypes in the offspring?

  • 3 BbEE
  • 3 bbEE
  • 1 Bbee
  • 1 bbee