What are the common chromosome banding techniques and what is the significance of banding techniques?

Band-banding dyeing means that chromosomes are dyed with specific dyes after a certain procedure, so that they show alternating light and dark or horizontal stripes with different shades on the long axis. This kind of transverse stripe is called chromosome band.

Each chromosome contains a certain number of bands, a certain arrangement order, a certain width, and different shades of dyeing or shading, which constitute the band type of each chromosome. The process of displaying chromosome bands is called chromosome banding.

Chromosome banding technology, which appeared in the late 1960s, provided a more effective method for chromosome research. Chromosome banding techniques can be divided into two categories: one is whole chromosome banding techniques, such as Q banding and G banding; The other is chromosome local banding techniques, such as J banding and C banding.

1968, Swedish scholar T.O. Caspersson (19 10 ——) first treated chromosome samples with the fluorescent dye chloromequine, and found that chromosomes can display fluorescent bands with different widths and brightness along their longitudinal axis due to different coloring. This band pattern of alternating light and dark is called Q-band. Q-belt is less affected by production technology and heat treatment, and the production effect is good, and the belt type is clear. However, due to the short duration of fluorescence, it is necessary to take photomicrography immediately. In addition, a fluorescence microscope is needed for observation, which can not be used in general laboratories. Later, the researchers found that if the chromosome sample was treated with salt, alkali, heat, trypsin or protease, urea and detergent, and then dyed with a dye called Giemsa, the chromosome could also show light and dark bands along its longitudinal axis, which was called G band. The g- banding pattern on each chromosome is basically the same as the Q- banding pattern. G-band dyeing is widely used in general laboratories because it can be observed under ordinary microscope because of the shortcomings of Q-band dyeing.

Using Q- banding, G- banding and other banding techniques, we can display the specific banding pattern of each human chromosome, which provides the necessary conditions for identifying and analyzing each chromosome.

Giemsa banding technique is the most commonly used technique in plant chromosome banding, among which C-banding and N-banding are widely used. The formation of C-band is considered that DNA with high repetitive sequence (heterochromatin) is easy to renaturate after acid-base denaturation, while DNA with low repetitive sequence and single sequence (euchromatin) does not exist, showing different staining reactions after Giemsa staining. This difference reflects the difference of chromosome structure.