What Is DNA Gel Electrophoresis?

After DNA molecules have been extracted, they need to be detected by electrophoresis technology to determine their quantity and quality. Since the introduction of agarose and polyacrylamide gels into nucleic acid research, gel electrophoresis technology that separates DNA according to its relative molecular mass has developed into an important experimental method for analyzing and identifying DNA molecules. Agarose or polyacrylamide gel electrophoresis is one of the nuclear techniques for genetic manipulation, which can be used to isolate, identify and purify DNA fragments. This technique is simple and fast to operate, and has become the basis of many common molecular biology research methods, such as DNA recombination, DNA nucleotide sequence analysis, DNA restriction endonuclease analysis, and restriction enzyme mapping.

When a molecule is placed in an electric field, they will move to the appropriate electrode at a certain speed. The migration speed of this electrophoretic molecule under the action of the electric field is called electrophoretic mobility. It is proportional to the strength of the electric field and the number of net charges carried by the electrophoretic molecule itself. In other words, the greater the electric field strength, the greater the number of net charges carried by the electrophoretic molecules, the faster the migration speed, and the slower the contrary. Since a non-reactive and stable support medium such as agarose gel and polyacrylamide gel is used in electrophoresis, thereby reducing convective motion, the electrophoretic mobility is inversely proportional to the coefficient of friction of the molecule . A known

(1) Agarose and polyacrylamide gel electrophoresis

Agarose is a linear polysaccharide polymer that is extracted from red algae product agar. When the agarose solution is heated to the boiling point and cooled to solidify, it will form a good electrophoretic medium, and its density is determined by the concentration of agarose. Chemically modified low melting point (LMP)

The resolving power of the gel is related to the type and concentration of the gel. The agarose gel can resolve DNA fragments in the range of 0.2 ~ 50kb, while the polyacrylamide gel has higher resolving power and can distinguish DNA fragments of smaller molecular weight , Its resolution range is 1 ~ 1000bp. The gel concentration affects the pore size of the gel medium. The higher the concentration,

The easiest and most common way to observe the DNA in a gel is to stain it with the fluorescent dye ethidium bromide. Ethidium bromide is a nucleic acid dye with flat molecules. Under high ionic strength, one ethidium bromide molecule is inserted approximately every 2.5 bases. In DNA

Pulsed field gel electrophoresis has been widely used in biological genotyping, molecular epidemiological research, apoptosis, tracking of infectious sources, veterinary epidemiological diagnosis assistance, food and public health, and chromosomal DNA isolation. ^[3]

Tracking the source of infection by gel electrophoresis

Pulsed-field gel electrophoresis is one of the useful techniques for tracing the source to evaluate the possible relationship between strains from different sources in the same event. When an outbreak occurs, in order to take targeted measures to prevent and control the outbreak reasonably and effectively, the root cause of the outbreak needs to be clearly identified. Pulsed-field gel electrophoresis can find key connections in seemingly disparate cases, track the source of infection, and ultimately achieve disease prevention and control. ^[3]

Gel electrophoresis molecular typing

At present (2012), pulsed-field gel electrophoresis is one of the widely accepted methods in molecular epidemiology at home and abroad, and is considered to be the "gold standard" for bacterial molecular biology technology. Compared with ribosome typing The typing ability of pulse field gel electrophoresis is stronger. Pulsed-field gel electrophoresis typing is the most common molecular typing method used in cholera epidemiological investigations at this stage. ^[3]

Molecular Epidemiology of Gel Electrophoresis

Pulsed field gel electrophoresis has become the most effective method in molecular epidemiological research because it has more advantages in distinguishing subspecies than phenotypic identification and Southern hybridization. Studies have shown that pulsed field gel electrophoresis is as effective as PCR fingerprinting in identifying outbreaks of nosocomial infections and has its own unique advantages. ^[3]

Application of gel electrophoresis in veterinary field

In 1996, some scholars carried out genome analysis of Mycobacterium bovis and other complex Mycobacterium tuberculosis by performing isozyme analysis and pulsed field gel electrophoresis. The results show that pulsed-field gel electrophoresis is a highly discriminating technique for the epidemiological study of M. bovis tuberculosis. It can culture and isolate M. bovis tuberculosis in animals with independent outbreaks of TB, and type The source of infection was identified, showing the possibility of multiple infections caused by different strains in a certain area. ^[3]