Epistasis Transitional Reasoning Practice

Questions

1. 1.

   In a certain flowering plant, flower color is regulated by two unlinked genes, P and C, functioning in a sequential biochemical pathway where enzyme P converts a colorless precursor into a red intermediate, and enzyme C converts the red intermediate into a deep purple pigment. Homozygous recessive alleles for either gene (pp or cc) produce completely non-functional enzymes, such that absence of active enzyme C halts the pathway at the red intermediate stage, while absence of active enzyme P leaves the petals white regardless of the alleles at the C locus. A plant breeder crosses two dihybrid purple-flowered plants (PpCc × PpCc) and collects 160 offspring. Based on this biochemical pathway, which of the following correctly identifies the expected phenotypic breakdown of the offspring?

   • A) 90 purple, 70 white, and 0 red
   • B) 100 purple, 30 red, and 30 white
   • C) 90 purple, 40 red, and 30 white
   • D) 90 purple, 30 red, and 40 white

Answers and step-by-step solutions appear after you finish the test.