R-banding highlights:
R-banding technique produces reverse pattern of G-banding using heat denaturation of chromosomes followed by Giemsa or acridine orange staining. It preferentially highlights GC-rich, gene-rich euchromatic regions that replicate early, contain CpG islands, H3K4 trimethylation and Alu repeats, regions pale in G-bands. Centromeres and AT-rich heterochromatin with H3K9 trimethylation stay pale. R-bands include many housekeeping genes showing high transcriptional activity. Because chromosome ends stain intensely, R-banding useful for detecting cryptic telomeric translocations, unlike C-banding which marks constitutive heterochromatin at centromeres and telomere specific staining.
Ref: Gardner Textbook: R-banding Highlights GC-rich Euchromatic Regions; NCBI Bookshelf Clinical Cytogenetics Methods