Two alleles determine flower color in the plant Datura: P determines purple; and p, white. The P locus is on the smallest chromosome, number 3. In plants trisomic for this chromosome, n + 1 pollen is never functional, and only half the n + 1 eggs are functional. Assume that P is always completely dominant to any number of p's, and that the locus is close to the centromere. What is the expected ratio of purple:white in the progeny of the following crosses?