[Campbell Biology P.339] Juanita was born with polydactyly six toes on each foot , a dominan... | Practice Question

Juanita was born with polydactyly six toes on each foot , a dominant trait. Her mother also has polydactyly, but her father does not. Two of her five siblings also have the trait. What must Juanita's genotype be for this character using D for the dominant allele ?

  • A: DD
  • B: Dd
  • C: dd
  • D: It cannot be determined from the information given.

Explanation

Juanita has the dominant trait polydactyly , so her genotype must be either DD or Dd. Her father does not have the trait, meaning his genotype is homozygous recessive dd . Therefore, Juanita must have inherited a d allele from her father. To express the dominant trait, she must have inherited a D allele from her mother. Thus, her genotype must be Dd.