Chromosome banding and compaction.

We have described a characteristic substructure of mitotic chromosomes, the chromosomal unit fibre, with lengths about five times the length of the corresponding metaphase chromosomes and a uniform diameter of 0.4 micrometer. In order to study the relationship of chromosome banding to chromosome compaction, methods have been devised to obtain banding patterns on chromosomal unit fibres, similar to G-band patterns of intact mitotic chromosomes. The total number of bands plus interbands per haploid human karyotype is estimated at about 3000. The banding pattern of chromosomal unit fibres indicates a certain resemblance to the normal G-banding pattern of human chromosomes even if the details indicate a short-range random distribution.