Northern blot vs southern blot

Northern blot vs southern blot

Northern blotting protocol

The identification of small DNA fragments separated by gel electrophoresis is known as Southern blot hybridization (Figure 1). The isolated DNA fragments are denaturated and blotted onto a nitrocellulose (or nylon) membrane sheet after electrophoresis. The gel is supported on a sponge in an alkali solution bath, and buffer is sucked through the gel and the sheet by paper towels stacked on top of the nitrocellulose sheet during the blotting. The buffer denaturizes the DNA and moves single-stranded fragments from the gel to the sheet’s surface, where they tightly bind. The bound single-stranded DNA fragments are peeled from the nitrocellulose sheet and placed in a sealed plastic bag or box with buffer containing a labelled DNA probe specific for the target DNA sequence. The sheet is exposed to the probe in a hybridization-friendly environment. The sheet is removed from the bag after hybridization, washed thoroughly to extract unhybridized probes, and viewed using autoradiography or ultraviolet light, depending on the labels used (radioactive of fluorescent). Northern blotting is a variation of Southern blotting in which RNA molecules instead of DNA are electrophoresed through the gel.

Northern blotting ppt

By assessing the specific gene expression rates during differentiation and morphogenesis, as well as in abnormal or diseased conditions, northern blotting can be used to observe cellular control over structure and function.


[number four] Northern blotting is a technique that uses electrophoresis to size-separate RNA samples before detecting them with a hybridization probe that matches part of or the entire target sequence. The term ‘northern blot’ refers to the transfer of RNA from an electrophoresis gel to a blotting membrane through capillary transfer. Northern blotting is the term used to describe the whole procedure. (5) The northern blot technique was created in 1977 at Stanford University by James Alwine, David Kemp, and George Stark, with contributions from Gerhard Heinrich. The term Northern blotting comes from its resemblance to the first blotting procedure, the Southern blot, which was named after biologist Edwin Southern. [two] The main difference is that the northern blot looks at RNA rather than DNA. [nine]

Northern blotting pdf

Only when the majority of the DNA molecules on an electrophoretic gel are the same size, such as after a PCR reaction or restriction digestion of a plasmid, do bands of DNA shape. In other cases, such as after restriction digestion of chromosomal (genomic) DNA, the digest will contain a large number of variable-sized fragments, resulting in a continuous smear of DNA rather than distinct bands. To detect the presence of a particular DNA sequence inside a smear of DNA isolated on an electrophoretic gel in this case, additional techniques must be used. A “Southern Blot” may be used to do this.
A Southern blot (also known as a Southern Transfer) is named after its inventor, Ed Southern. In the first step, restriction enzymes are used to digest DNA, which is then separated using gel electrophoresis (as discussed above). The DNA is then transferred to the membrane in its separated form (bands or smear) by drawing the liquid out of the gel (Figure (PageIndex1)). By briefly exposing the blotted DNA to UV light, the DNA is normally covalently bound to the nylon membrane. The delicate gel would fall apart over the next two steps in the process if the DNA was not transferred to the durable membrane. The membrane is then immersed in a solution to denature (turn double stranded DNA into single stranded DNA). After that, a hybridization solution with a limited amount of single-stranded probe DNA that is complementary in sequence to a target molecule on the membrane is used. If the hybridization is done correctly, the probe DNA can form a stable duplex only with those DNA molecules on the membrane that are exactly complementary to it. After that, the unhybridized probe is washed away, and any residual radioactive or fluorescent signal is detected in a distinct band. Within the mixture of DNA fragments, the band denotes the presence of a specific DNA sequence.

Western blot vs southern blot vs northern blot mcat

In a complex mixture of similar molecules, different blots are used to recognise the presence of one unique target molecule (DNA, RNA, or protein). Blotting is the process of transferring macromolecules (nucleic acids and proteins) from a gel to the solid surface of an immobilized membrane for detection. A common workflow can be used in all blotting techniques. Initially, an electrophoretic technique based on the movement of macromolecules in an electric field is used to isolate molecules (or protein and nucleic acid fragments) by size on a gel. The separated molecules are then transferred to a solid membrane (nitrocellulose, nylon, PVDF, etc.) that is designed to immobilize the target molecule of interest. During an incubation stage that promotes hybridization, end-users may add “labels” (radiolabel, fluorescent label, reporter enzyme label) to the immobilized targets with probes that are sequence-specific or shape-specific to the target molecule of interest (either DNA, RNA, or protein). This hybridized complex, which consists of a bound probe and is called a “immobilized target molecule—label/probe,” can be identified and visualized later using various imaging methods. We’ll look at some of the differences between Southern, Northern, and Western blots, which are used to detect DNA, RNA, and protein, respectively.