Diagnostic Methods in Biotechnology: Blotting
Discover the fundamental role of blotting techniques in molecular biology research, their direct impact on diagnostics, and cutting-edge biotechnology innovations.
What is blotting?
Blotting is a technique widely used in molecular biology and biotechnology for characterizing various biomolecules, including DNA, RNA, and proteins.
“Blotting” is a common term used for all three types of molecules.
So how did we come to use a single term for all of them?
Let’s first focus on the word “blot.”
What is a “blot”?
Dictionaries define “blot” as a “stain” or “mark.” It also has a verb form, which some dictionaries explain as “to dry ink with blotting paper.”
So what does this technique in molecular biology and biotechnology have to do with that?
Actually, the connection is very simple:
If you separate molecules by size or charge using a technique such as electrophoresis, which we’ve discussed in our other articles, and then press an absorbent paper against them, the traces of these molecules will appear on the paper.
Just like pressing absorbent paper onto an ink stain.
That is why this technique is called “blotting.”
The absorbent paper in question here is a special type of paper, such as nitrocellulose or PVDF.
So, what is blotting used for?
It is used in clinical diagnosis; for example, the presence of certain proteins can be detected using a special “blotting” technique called Western Blot.
Or, if an increase in the expression of a gene occurs as a result of a disease, a special “blotting” technique called Northern Blot can be used to measure its levels at the RNA level.
It is used in molecular biology, genetics, and biotechnology research laboratories; for example, a specific “blotting” technique called Southern Blot can be used to verify cloned DNA.
Of course, there are other methods besides “blotting” for all these purposes today; but those are the subject of another article.
What are the different types of “blotting” mentioned above, and what are their advantages and disadvantages?
1. Southern Blotting (DNA Analysis)
If you are going to use the “blotting” technique for DNA characterization, this is known as a Southern Blot.
Advantages: DNA molecules are programmable because they consist of A and T, and G and C nucleotides that can form complementary pairs. The Southern Blot utilizes this principle of complementarity and therefore offers high specificity.
Disadvantages: A large amount of starting DNA is required to run and separate the DNA on a gel and to form the “blot.” Additionally, the process is time-consuming. Although it is no longer mandatory, the occasional use of radioactive probes still poses certain risks.
2. Northern Blotting (RNA Analysis)
If you are characterizing RNA, the technique is called Northern Blot.
Advantages: As with DNA samples, it has high specificity, and a key advantage here is that it allows for the direct measurement of gene expression levels.
Disadvantages: Because RNA molecules are not as stable as DNA molecules, this method is susceptible to degradation; however, this disadvantage stems from the nature of the molecule used rather than the technique itself.
3. Western Blotting (Protein Analysis)
If this technique is used for the characterization of proteins, it is referred to as a Western Blot.
Advantages: It is highly advantageous because it allows for the accurate determination of protein size on the gel while simultaneously enabling the detection of antigen-antibody interactions in the regions of the gel corresponding to the expected sizes of the biomolecules.
Disadvantages: The measurement results are not considered quantitative; they are reported as semi-quantitative. Therefore, this method is primarily used to gain a qualitative understanding of the subject.
Did you also find it interesting that these are referred to by directional names like North, South, and West?
The first “blotting” method to be applied was the Southern Blot.
The method is named after the researcher who developed it and published it in 1975: Edwin Southern.
Subsequently, in 1977, Alwine and colleagues published the “blotting” method for RNA molecules. Today, this is known as the Northern Blot.
In a paper published by Towbin and colleagues in 1979, the “blotting” technique was adapted to proteins for the first time. This is known as the Western Blot.
At Rapdi Biotech, our research focuses on aptasensor development.
The Southern Blot, Northern Blot, and Western Blot methods mentioned above can be used to characterize molecules that bind to the target during the aptamer SELEX selection process or to characterize the target molecules themselves.
Please remember that you can contact Rapdi Biotech for any support related to aptasensor development.
References:
Southern, E. M. (1975). Detection of specific sequences among DNA fragments separated by gel electrophoresis. Journal of Molecular Biology, 98(3), 503-517.
Alwine, J. C., Kemp, D. J., & Stark, G. R. (1977). Method for detection of specific RNAs in agarose gels by transfer to diazobenzyloxymethyl-paper and hybridization with DNA probes. Proceedings of the National Academy of Sciences, 74(12), 5350-5354.
Towbin, H., Staehelin, T., & Gordon, J. (1979). Electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets: procedure and some applications. Proceedings of the National Academy of Sciences, 76(9), 4350-4354.
Brown, T. (2001). Southern blotting. Current Protocols in Immunology, Chapter 10:Unit 10.6A. doi: 10.1002/0471142735.im1006as06.
He, S. L., & Green, R. (2013). Northern blotting. Methods in Enzymology, (530), 75-87. doi: 10.1016/B978-0-12-420037-1.00003-8.
Zubair, M., & Launico, M. V. (2026). Western Blot: Principles, Procedures, and Clinical Applications. StatPearls. StatPearls Publishing. Available from: nih.gov
Merriam-Webster Dictionary. merriam-webster.com [Accessed July 8, 2026].
Vocabulary.com Dictionary. vocabulary.com [Accessed July 8, 2026].
Disclaimer:
The information provided in this article is for educational and informational purposes only, based on current scientific literature. It does not constitute medical advice, diagnosis, or treatment. For any medical concerns or diagnostic needs, always consult with a qualified healthcare professional.