Figure 1.

(A–E) Models of meiotic recombination in diploids and autotetraploids. The left column shows diploids and the right column tetraploids. (A) Replication of chromosomes. (B) Pairing of chromosomes into bivalents (diploids, tetraploids) and quadrivalents (tetraploids). (C) Recombination of paired chromosomes. See also Figure 2. (D) Distribution of (possibly) recombined chromosomes into gametes. (E) Crossing of gametes into seeds. Shaded circles show overall numbers of possibilities in that step. 1, p, p₁, and p₂ on the left sides of steps denote probabilities from previous steps. Formulas on the right sides of steps denote probabilities up to and including the current step. Alternatives are separated by vertical bars in square brackets, r is the frequency of recombination between the two marker loci, q is the recombination frequency between the centromere and the centromere-proximal marker, τ is the quadrivalent-to-bivalent ratio, and p_DP and p_PC are the probabilities of having a partner switch between the markers and between the centromere-proximal marker and the centromere, respectively. f(p_DP, p_PC, r, q) denotes a function of the parameters indicated.