CHROMOSOME BANDS - FLAVORS TO SAVOUR

The mammalian chromosome is longitudinally heterogeneous in structure and function and this is the basis for the specific banding patterns p roduced by various chromosome staining techniques. The two most freque ntly used techniques are G, or Giemsa banding and R, or reverse bandin g. Each type of stained band is characterised by variations in gene de nsity, time of replication, base composition, density of repeat sequen ces, and chromatin packaging. It is increasingly apparent that R and G bands, which are complementary to each other, represent separate comp artments of the euchromatic human genome, with R bands containing the vast majority of genes. R bands are also more GC-rich, contain a highe r density of Alu repeats, and replicate earlier in S phase, than G ban ds. These properties may be interdependent and may have coevolved.