Fig. 6. Chromosome analysis in spreads of male meiocytes in wild type and duet. (A-J) Wild type; (K-W) duet. (A,K) Chromosomes first become visible as elongated strands during leptotene. (B,L) Synapsis takes place during zygotene. (C,M) Synapsis is complete at pachytene and chromosomes have a shorter and thicker appearance. (D) Diplotene stage, when bivalents have undergone partial decondensation. (E) Late diakinesis showing five pairs of chromosomes with chiasmata at their ends. (F) Metaphase I stage showing five condensed bivalents arranged on a metaphase plate. (G) Telophase I: five chromosomes at each end are separated by an organelle band. (H) Metaphase II. (I) Anaphase II. (G-I) Arrows indicate the densely compacted organelle band. (J) Telophase II where four groups of five chromosomes each have separated. (N) First apparent visible defect in duet at diplotene. Chromosomes start to look diffuse and two bivalents have undergone partial desynapsis (arrowheads). (O) A more severe form of desynapsis can be observed in the majority of bivalents. (P,Q) Disorganized diakinesis in duet with diffuse chromosomes including the centromeric region. (R,S,T) Metaphase I. (U) Anaphase I. (V) Defective anaphase I stage with fragmented chromosome and laggards. (W) Telophase I. The organelle band is absent. Scale bars: 12.5 µm.

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