[Campbell Biology P.324] If a testcross between a purple-flowered pea plant unknown genotype... | Practice Question

If a testcross between a purple-flowered pea plant unknown genotype and a white-flowered pea plant pp results in offspring that are 1/2 purple and 1/2 white, what is the genotype of the purple-flowered parent?

  • A: PP
  • B: Pp
  • C: pp
  • D: It cannot be determined from this cross.

Explanation

As shown in the 'Predictions' part of Figure 14.7, a cross between a Pp parent and a pp parent is expected to produce 1/2 Pp purple and 1/2 pp white offspring. Therefore, observing this 1:1 ratio reveals the unknown parent's genotype to be heterozygous Pp .