An illustration of meiotic prophase I progression in wheat highlighting factors that influence the distal bias of CO distribution and frequency. One stylised pair of wheat chromosomes is represented within the nuclear envelope in which the coordination of telomere/centromere clustering, chromosome axis maturation, chromosome pairing, synapsis and homologous recombination occur in the context of chromatin cycles of expansion and contraction. By Early G2, chromosomes have been replicated and are now a pair of sister-chromatids that are held together by the cohesion complex of proteins that form the axis where ASY1 begins to load. At late G2, the ASY1 protein becomes linear towards the telomeres and double-strand breaks are detected by γH2A.X labelling. During early leptotene, strand exchange proteins RAD51 and DMC1 localise to the linear ASY1 axis towards the telomeres and γH2A.X labelling is detected in the interstitial and centromere proximal regions. At this stage the telomeres have clustered into the bouquet and are located at the nuclear envelope. At late leptotene, class I CO proteins MSH4 and MSH5 are first observed co-localising with ASY1 adjacent to the telomeres and DMC1 and RAD51 are present in the interstitial/peri-centromeric regions. At this stage the chromosomes are fully paired. Early zygotene is characterised by the installation of the synaptonemal complex protein ZYP1 in the sub-telomeric regions and depletion of ASY1 as well as co-localisation of class I CO protein HEI10. MSH4 and MSH5 are observed in the interstitial/peri-centromeric regions. At mid-zygotene, ZYP1 has polymerised ∼50% of the chromosome pairs and HEI10 is observed in the majority of ZYP1/ASY1 labelled sites. At late zygotene, ZYP1 polymerisation is <75% and small HEI10 pairs of foci coalesce into singular, larger foci. At pachytene, ZYP1 polymerisation is complete and ASY1 is mostly depleted from the chromosome axis. HEI10 marks designated CO sites that form predominantly in the distal regions where the euchromatin is hyper-abundant. All prophase I chromosomes contain loops with euchromatin and heterochromatin abundant regions, but for ease of presentation these are only shown at pachytene.