Fractions of DNA of differing base composition
(isochores) produce banding patterns on human metaphase
chromosomes with the most GC-rich fractions
highlighting T-bands (Saccone et al., 1993). Molecular
analyses on a finer scale reveal that, although there is a
general tendency for G-bands to be quite AT-rich, R-bands
can contain both AT-rich isochores and GC-rich isochores.