[Campbell Biology P.327] In the same cross PpYyRr x Ppyyrr , what is the fraction of offspri... | Practice Question

In the same cross PpYyRr x Ppyyrr , what is the fraction of offspring predicted to exhibit at least two recessive phenotypes?

  • A: 1/16
  • B: 3/16
  • C: 6/16 or 3/8
  • D: 9/16

Explanation

The text walks through this exact calculation. You must list all genotypes with at least two recessive traits ppyyrr, ppYyrr, Ppyyrr, PPyyrr, ppyyRr , calculate the probability of each using the multiplication rule, and then add them together using the addition rule. The probabilities are 1/16 + 1/16 + 2/16 + 1/16 + 1/16 = 6/16 = 3/8.