What is G-banding? What regions of the chromosome (e. g. base composition, condensed or open, early or late replicating) are stained darkly when this technique is used?

G-banding or Giemsa banding is a technique used to study the chromosomes by staining then at condensed stage. The visible karyotype can be used by this technique. The genetic diseases can be easily identified by this G banding technique.

The base composition of the genes (nucleotide) are stained by the dye known as Giemsa stain. The nitrogenous base adenine and thymine of the heterochromatic region of chromosome stained darkly in this technique. The darkly stained area is generally gene poor area.