The classic chromosomal banding pattern arises from the irregular folding path of the AT-queue. Loops are not directly observed by fluorescence microscopy but inferred and the structural relationship of neighboring loops and their packaging mode is not known.
Sister chromatids relate to each other by mirror symmetry.
The top and bottom optical sections reveals the opposite handedness of the scaffold coil. Although individual loops cannot be observed by confocal microscopy, they are graphically indicated in an oversimplified fashion in the model based on a number of considerations. We do not actually know the precise packaging mode of the loops along the AT-queue. They arise from the irregular folding path of the AT-queue and are a consequence of the loop model . R-bands are known to replicate early and to be genetically more active.