Southern Blot
Southern blotting is a molecular biology technique used to detect specific DNA sequences in a complex mixture by transferring size-separated DNA fragments from an agarose gel onto a membrane (nitrocellulose or nylon), followed by hybridisation with a labelled probe complementary to the target sequence. The method, developed by Edwin Southern in 1975, enables researchers to determine the presence, size, and relative abundance of a target gene. It is used in genetic disease diagnosis, forensic analysis, and studies of gene copy number and rearrangements.
Comparison of Blotting Techniques
| Technique | Molecule Detected | Separation Method | Probe Type | Named After |
|---|---|---|---|---|
| Southern Blot | DNA | Agarose gel electrophoresis | Labelled DNA/RNA probe | Edwin Southern |
| Northern Blot | RNA (mRNA) | Denaturing agarose gel | Labelled DNA/RNA probe | Named by analogy |
| Western Blot | Protein | SDS-PAGE | Labelled antibody | Named by analogy |
| Eastern Blot | Post-translational modifications | SDS-PAGE | Lectin / antibody | Named by analogy |
| Far-Western Blot | Protein–protein interactions | SDS-PAGE | Labelled protein bait | Named by analogy |
Interactive Tools
Khan Academy — Southern Blot
Step-by-step explanation of gel electrophoresis and blotting techniques
Open ToolNCBI PubMed — Southern Blotting Protocols
Access original research papers and protocol updates for Southern blotting
Open ToolThermo Fisher Learning Center
Detailed Southern blot protocol guide with reagent selection tips
Open Tool
Wikimedia Commons, CC BY-SA
Related Terms
Recombinant DNA
Recombinant DNA (rDNA) is artificially engineered DNA formed by joining sequences from two or more different organisms using molecular biology techniques such as restriction endonucleases and DNA ligase. The resulting hybrid molecule can be introduced into a host cell where it replicates and, if properly constructed, directs the synthesis of a desired protein. rDNA technology underlies the production of medicines such as human insulin, erythropoietin, and growth hormone.
Gel Electrophoresis
Gel electrophoresis is a laboratory technique used to separate macromolecules — primarily DNA, RNA, or proteins — by size and charge as they migrate through a porous gel matrix under the influence of an electric field. Negatively charged nucleic acids migrate toward the positive electrode (anode), with smaller fragments travelling faster and further than larger ones, producing a pattern of bands that can be visualised by staining with ethidium bromide or SYBR Green and exposing to UV light. Gel electrophoresis is one of the most widely used techniques in molecular biology, underpinning applications from forensic DNA profiling and paternity testing to restriction mapping, PCR product verification, and Southern blotting.
Named after Edwin Southern (born 1938), a British biologist at the University of Edinburgh who developed the technique in 1975. The analogous techniques for RNA (Northern) and protein (Western) were named humorously by the scientific community.