Differences Between Western, Northern, and Southern Blot

Your students are sure to have a learning curve remembering the differences between Western, Northern, and Southern Blot. In this article, we will lay out their characteristics in a way that can ease your students’ confusion.

Here are the three facts your students will struggle to remember until they have hands-on experiences with experiments from Modern Bioscience:

Western blot identifies proteins.
Southern blot identifies DNA.
Northern blot identifies RNA.

You can reinforce student understanding of Western blotting in EXP-801: Serum Proteins and the Western Press-Blot. Your students can use Western blotting in an experiment to develop their understanding of the immune system.

With Modern Bioscience, your students will also have opportunities to identify viral DNA by rapid Southern blotting. And you can easily locate laboratory products for advanced classes to use Northern blotting to reveal important information about the identity, size, and abundance of RNA to permit a deeper understanding of gene expression.

What Do Your Students Need to Know About Western Blot?

Investigators use Western blotting to identify a specific amino acid sequence in a mixture of proteins. The first step of Western blotting is electrophoresis to separate proteins into bands on the basis of molecular weight. Then the bands are transferred separately onto a membrane by blotting.

The bands are then incubated with a primary antibody that binds with the target protein. A secondary antibody that is labeled with an enzyme such as horseradish peroxidase is added to the band to detect the first antibody. If the first antibody is present in a band, then the action of the enzyme makes the presence of the protein visible as the membrane is incubated.

Western blotting is used for definitive testing of Lyme disease, Creutzfeldt-Jakob disease, and herpes.

What Do Your Students Need to Know About Southern Blot?

Southern blotting identifies a specific DNA sequence in a mixture of DNAs. It also begins with electrophoresis.

Electrophoresis separates bands of DNA on the basis of molecular size. The investigator places a nitrocellulose membrane on the gel used for electrophoresis. The separated bands of DNA are transferred to the membrane by capillary action.

Then the target sequence, if present on the membrane, is hybridized with a specific, labeled oligonucleotide sequence known as the hybridization probe. This nucleotide sequence is 100 to 500 base pairs long. It is a single-stranded DNA molecule. This process is very sensitive to temperature and salt concentration.

The practical applications of Southern blotting include paternity testing, victim identification, and DNA fingerprinting. Southern blotting can also identify pathogens and test for genetic diseases.

What Do Your Students Need to Know About Northern Blot?

Very few biology classes will do Northern blotting. Modern Bioscience does not offer an experiment utilizing this technique. However, students need to know that this method also uses electrophoresis and capillary transfer to a membrane for hybridization to detect specific sequences of RNA. Students who master the technique for Southern blotting will not have trouble using Northern blotting later.

What Knowledge Should Students Retain About Blotting Techniques?

Western blotting, Southern blotting, and Northern blotting are all techniques used to identify a particular type of macromolecule within a sample.

All three blotting techniques involve electrophoresis, transfer, and detection.
All three blotting techniques require denaturation and blocking with a corresponding molecule.
Each technique has numerous applications in medicine and biotechnology.

With products from Modern Biology, you can take your students beyond the mere retention of vocabulary words and testable facts to understanding scientific methods and critical thinking.

For forty years since Modern Biology Inc. was founded by Dr. John Anderson, we have followed the same fundamental pedagogical principles.
Every experiment manufactured by Modern Biology matches a clear and concise lesson, with notes to help teachers prepare for it. Teachers can also develop test questions from the lesson guide.

Every experiment kit made by Modern Biology supports scientific thinking. Students test their hypotheses. They never just watch demonstrations. They are never limited to facts and vocabulary.
Every Modern Biology helps students develop the manual dexterity and note-taking skills that they will carry to future study and their careers. Modern Biology is developed by working scientists for future working scientists.
Every Modern Biology kit includes all the reagents and test materials teachers need for their laboratory exercise. There are no ordering separate reagents, fussing about missing shipments, or checking out lab materials from the supply room. Modern Biology supplies the safe, non-toxic, reliable reagents and measurement materials you need for every laboratory exercise. And because every Modern Biology experiment is available at a fixed cost, it’s easier to budget your supply cost for each class for each school term.

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