The main difference between Southern Blotting and Western Blotting is that Southern Blotting is a technique that is used to detect a specific DNA fragment in a given sample whereas Western Blotting is used to find out a specific protein in a given sample.
Southern Blotting vs. Western Blotting
Blotting is a technique that is used by scientists to separate different types of molecules from a mixture or sample. In this technique, macromolecules like nucleic acids (DNA and RNA) and proteins in a mixture move through a slab of gel. Here, minute particles will move faster than the bigger ones. These molecules are pressed against the surface of an immobilized membrane which transfers the molecules onto the membrane. There are different types of blotting on the basis of detection of specific material, i.e., southern blotting, northern blotting, and western blotting. Southern blotting is the type of blotting that is used to detect DNA while western blotting is used to find out protein. Southern blotting was developed by Edward M. Southern in 1975. So, it is known as Southern blotting. On the other hand, western blotting was developed by George Stark’s group at Stanford University in 1979. This name was used to match with southern blotting. Southern blotting is used to find out a specific DNA sequence whereas, western blotting is used to find out a specific amino acid or protein sequence.
What is Southern Blotting?
Southern blotting is the oldest blotting method that was given by Edwin Southern thus, named as southern blotting. It is used to find out a specific sequence of DNA in a given sample or mixture. Steps involve during southern blotting are electrophoresis, transfer, and detection of specific sequences. First of all, DNA is fragmentized with the help of specific restriction enzyme. Then desired DNA fragments are separated through gel electrophoresis. These fragments are denatured with the help of an alkaline solution, e.g., NaOH, etc. to separate the two DNA strands. These single-stranded DNA fragments then transferred on a membrane through the process of blotting. This membrane-bounded DNA is then treated with a labelled probe. This probe will attach to its complementary strand on the membrane DNA which can be visualized by autoradiogram etc.
What is Western Blotting?
Western blotting method was invented by George Stark’s group at Stanford University that is used to identify a specific sequence of amino acids in the protein. It is also known as protein blot or immune-blotting. The steps during western blotting are electrophoresis, transfer, and detection of specific proteins. First of all, homogenize the mixture. Then separate the molecule of interest with the help of electrophoresis. Transfer these molecules on the membrane and identify the specific protein by using specific probe.
- A technique that is used to find out a specific DNA sequence in a given mixture is known as southern blotting whereas, a technique that is used to find out a specific amino acids sequence of the protein in a given mixture is known as southern blotting.
- Southern blotting was developed by Edward M. Southern in 1975 so, known as southern blotting. On the other hand, western blotting was developed by George Stark’s group at Stanford University in 1979.
- Southern blotting is used to find out a specific DNA sequence. Conversely, western blotting is used to find out a specific amino acid or protein sequence.
- Southern blotting works on the principle of hybridization on the flip side; western blotting works on the principle of immunodetection method or antigen-antibody interaction.
- A single-stranded DNA or sometimes RNA is used as a probe in Southern blotting on the other side, in western blotting primary and secondary antibodies are used as a probe.
- Agarose gel electrophoresis is used in southern blotting while SDS PAGE/ Polyacrylamide gel used to separate proteins in western blotting.
- Southern blotting follows capillary transfer procedure, on the other hand; western Blotting follows electric transfer procedure.
- During Southern blotting, the sample needs to be denaturated, whereas, during western blotting, the sample should be in its native state.
- No any step like blocking is involved in southern blotting on the flip side, during western blotting, nonspecific antibody sites are blocked on the nitrocellulose paper with the help of milk powder or bovine serum albumin (BSA).
- Common labeling methods that are used in southern blotting are the use of chromogenic dyes or radiolabelling or fluorescent labeling etc. while, labeling methods used in western blotting are the use of fluorescently labeled antibody or radiolabelling, chromogenic dyes or formation of diaminobenzidine, etc.
- Detection of light, Autoradiograph, and Changes in color are used as detection methods in southern blotting, whereas, detection methods in western blotting are changes in color and detection of light, etc.
- Southern blotting is used in DNA detection, paternity testing, DNA fingerprinting, for victim identification, for identifying criminals, to find infectious agents and to identify mutation or gene rearrangement, etc. Conversely, western blotting is used to find the number of protein in a mixture, to detect the presence of HIV, virus, and bacteria, etc. in the serum, to find out defective proteins and used as a definite measure for herpes, hepatitis B, Lyme disease, and Creutzfeldt-Jacob disease, etc.
Above discussion summarizes that southern blotting is the oldest blotting technique used to find out specific DNA segment in a sample while western blotting was discovered latter and used to identify a specific sequence of amino acids or a specific protein.