Introduction to Southern blotting:

Southern blotting is a technique used to analyze and identify specific DNA sequences in a sample. The method is based on the principle of DNA separation by electrophoresis and DNA detection by hybridization. It has been widely used in molecular biology, genetics, and medical research for the detection and characterization of DNA.

Discovery of Southern blotting:

This technique was first proposed by the British molecular biologist Edwin Southern in 1975. He used the method to analyze DNA samples and named it Southern blotting as a reference to his own name.

Principal of Southern blotting:

The principle of Southern blotting is based on the separation of DNA by electrophoresis and detection by hybridization. DNA is separated by size and charge in an electrophoresis gel, and then transferred to a membrane, such as nitrocellulose or nylon. The membrane is then incubated with a specific DNA probe, which is a single-stranded DNA or RNA molecule that is complementary to the sequence of interest. The probe binds to the DNA of interest through base-pairing, and then a detection method is used to visualize the hybridized DNA.

Procedure (Step-wise):

1. Sample preparation: The DNA sample is prepared by extracting it from the source tissue or cell. The sample is then digested with restriction enzymes to generate fragments of DNA with known sizes.
2. Electrophoresis: The DNA sample is loaded onto an electrophoresis gel, such as agarose gel, and an electric field is applied. The DNA fragments migrate through the gel based on their size and charge, resulting in a separation of the DNA.
3. Transfer: The DNA fragments are transferred from the gel to a membrane, such as nitrocellulose or nylon. This process is called electroblotting or Southern blotting.
4. Denaturation: The DNA fragments on the membrane are denatured by heating or chemical treatment to separate the double-stranded DNA into single strands.
5. Blocking: The membrane is blocked with a solution containing a non-specific DNA to prevent non-specific binding of the probe.
6. Hybridization: The membrane is incubated with a specific DNA probe, which is a single-stranded DNA or RNA molecule that is complementary to the sequence of interest. The probe binds to the DNA of interest through base-pairing.
7. Detection: The hybridized DNA is detected by a suitable method such as radioactive or non-radioactive labeling.
8. Analysis: The band on the membrane that corresponds to the DNA of interest is analyzed and the DNA is identified.

Applications:

1. Medical research: Southern blotting is used to detect and analyze DNA in various diseases such as cancer, genetic disorders, and infectious diseases.
2. Genetic engineering: It is used to analyze and purify DNA for genetic engineering and gene therapy.
3. Quality control: This technique is used to ensure the quality of DNA samples used in research and industry.
4. Diagnostics: Southern blotting is used in the diagnosis of various diseases such as sickle cell anemia and thalassemia.
5. Environmental monitoring: This process is used to detect and analyze DNA in environmental samples such as water and soil.

In conclusion, Southern blotting is a powerful technique that is widely used in molecular biology, genetics, and medical research. The method is based on the separation of DNA by electrophoresis and detection by hybridization. Southern blotting has many applications in various fields such as medical research, genetic engineering, quality control, diagnostics, and environmental monitoring.