Fig. 4. Chromosome analysis in various stages of female meiosis in wild type and dyad plants. (A-F) Wild type, (G-M) dyad. (A,G) Chromosomes first become visible as elongated strands during leptotene. (B) Synapsis takes place during zygotene and synapsed regions can be detected as thicker segments. (C) Synapsis is complete at pachytene and chromosomes have a shorter and thicker appearance. (D) Late diplotene stage, when bivalents have undergone partial decondensation of the arms but not centromeric regions and the two halves of bivalents can be seen. (E) Metaphase stage showing five condensed bivalents. (F) Dyad stage after completion of meiosis 1. Each of the two cells contains 5 univalents at prometaphase 2. (H) In dyad, 10 univalents are observed instead of 5 bivalents indicating failure to undergo synapsis. (I) The univalents undergo partial decondensation of the arms. (J) Metaphase plate containing 10 chromosomes. (K) Anaphase 1 resembles an equational division. (L) Dyad stage at prometaphase 2 after completion of meiosis 1. (M) Magnification of the upper cell of the dyad in L. The cell is estimated to contain 10 chromosomes (white arrows). Black arrowhead indicates a chromosome with a pair of sister chromatids suggesting an additional round of replication has occurred. Bar: 5 µm (J,M) and 10 µm (A-I,K,L).