A model that accounts for chromosomal banding. The microscopic appearance of chromosomes during mitosis (metaphase) displays chromomeres and interchromomeres, i.e. G bands (Giemsa stain) and R bands (Reverse) respectively; the former are characterised as AT-rich and gene-poor and by late replication, and the latter as GC- and gene-rich and by early replication. The DNA is presumably organised into wide spring-like coils from which 100kb G loops extend parallel to the chromosome axis (G bands), extended DNA sequences from which larger loops extend perpendicular to the chromosome axis (R loops), and AT-rich sequences called matrix-attachment or scaffold-associated regions that anchor the G and R loop regions and create the characteristically stained bands.