[Campbell Biology P.323] Why do organisms with genotypes PP and Pp have the same phenotype p... | Practice Question

Why do organisms with genotypes PP and Pp have the same phenotype purple flowers ?

  • A: Because the P allele is dominant and the p allele is recessive.
  • B: Because both genotypes produce the same amount of purple pigment.
  • C: Because phenotype is determined by the number of alleles, not their type.
  • D: Because they are both true-breeding.

Explanation

This is the principle of dominance. The text states, 'if the two alleles at a locus differ, then one, the dominant allele, determines the organism's appearance; the other, the recessive allele, has no noticeable effect'. Since P purple is dominant, both PP and Pp genotypes result in the purple phenotype.