Figure 6.
A model of the DNA structure of diploid, triploid and tetraploid cells. In diploid cells (a, b and c), DNA is linked as homologueous chromosomes arranged to point symmetrically (a). Circles 1 and 6, 2 and 5, and 3 and 4 represent sets of short, medium‐sized and long chromosomes, respectively. 1–6 and 1* to 6* represent paternal and maternal haploid sets, respectively. Homologous chromosomes cannot close each other in the folded structure (Rabl orientation) in G 0 /G 1 phase (b). (c) is the replicated DNA structure in the G 2 phase. Tetraploid cells are made through the linking of maternal 1* and paternal 1 DNA between two double‐stranded chains (arrow 2–4, e). Homologous chromosomes can approach each other allowing DNA hybridization in the Rabl orientation of tetraploid cells (d), producing a possible tetraploid‐diploid transition (arrow 4–2). (f) is the replicated DNA structure in the G 2 phase of tetraploid cells. When two haploid sets of 1–6 (or 1*‐6*) hybridize and escape DNA replication, triploid cells are produced through cell division (arrow 4–3, g or h). Homologous chromosomes cannot close each other in the Rabl orientation of triploid cells (i). (j) is the replicated DNA structure at G 2 in triploid cells.