每一个染色体臂has a unique banding pattern that is used for its identification and for the detection of potential structural abnormalities. The chromosome banding pattern is comprised of alternating light and dark bands that appear after digested with an enzyme (trypsin) stained with a dye (Giemsa or Leishman). A landmark is a consistent and distinct morphologic region of achromosome. These regions are divided into bands which are further divided into sub-bands, used for naming the chromosomes. Example: Xp22.3 = X chromosome, short arm region 2, band 2, sub-band 3.

Figure 1.Chromosome banding