The Southern Blot

The northern blotting technique is similar to the Southern blotting technique with the exception that northern blots detect specific sequences of RNA, not DNA. 

A similar analysis could be made for a number of other diseases. Point mutations are usually defined by sequencing the gene in question, though occasionally, if the mutation destroys or creates a restriction enzyme site, the technique of restriction fragment analysis can be used to pinpoint the lesion. Deletions or insertions of DNA larger than 50 bp can often be detected by the Southern blotting procedure. 

In 1987, CL started to be applied in DNA hybridization assays as an alternative to the use of radioactive tags. These assays are based on the specificity of a binding process that of DNA strands for each other. An unknown DNA can be identified with the Southern blot method in which the strands of the analyte are separated and allowed to interact with labeled probe DNA strands on nitrocellulose filter paper. If the label on the probe is detected, the DNA can be identified and, in some cases, quantitated. Conventionally, radioactive tags were used be-... 

RFLP analysis by the Southern blot procedure and detection with probe specific for each VNTR are the basis of DNA fingerprinting. Using just four DNA probes, paternity can be excluded with a cumulative probability of 99.9% (J2). 

The Southern blot reveals not only the presence of a particular sequence, but also the size of the restriction fragment in which it lies. The size, in turn, is determined by the distribution of nearby restriction sites and so reflects the DNA sequence. 

Figure 3.24 Restriction fragments from digestion of two samples of DNA. These are produced as a result of the activity of restriction enzymes on the samples of DNA and separation of the fragments by the Southern blotting technique (Appendix 3.12). Numbers refer to the length of the fragments, (i.e. number of nucleotides).

Another variant of the hybridization assay is the Northern blot. Here it is RNA, not DNA, that is separated on a slab gel and transferred to a membrane. In the original version of the method, a special chemically treated cellulose membrane was used to hold the RNA, since nitrocellulose does not normally bind RNA. However, conditions have now been found where nitrocellulose will indeed retain RNA molecules. Nylon membranes can also be used. Radiolabeled DNA probes and autoradiography are then employed as above in the Southern blot method. The method is often useful in studying how levels of RNA species in a cell vary with stages of development and differentiation. 

FIGURE 1 The Southern blot procedure, as applied to DNA fingerprinting. This procedure was named after Jeremy Southern, who developed the technique. 

Correct answer = E. Both the father and mother must be carriers for this disease. The son must have inherited a mutant allele from each parent Because he shows only the 3 kb band on the Southern blot the mutant allele for this disease must be linked to the 3 kb band for both parents. The normal allele must be linked to the 4 kb band iri both parents. Because the daughter inherited the 4 kb band from both parents, she must be homozygous normal for the hexosaminidase A gene. 

El 1. The name Western blot is derived from other blotting procedures called the Southern blot (developed by Earl Southern) and the Northern blot. What are the differences among these three types of blotting techniques and what is the purpose of each ... 

Southern blotting. A method for detecting a specific DNA restriction fragment, developed by Edward Southern. DNA from a gel electrophoresis pattern is blotted onto nitrocellulose paper then the DNA is denatured and fixed on the paper. Subsequently, the pattern of specific sequences in the Southern blot can be determined by hybridization to a suitable probe and autoradiography. A northern blot is similar, except that RNA is blotted instead onto the nitrocellulose paper. 

In a sequence of events reminiscent of the Southern blot evolution into the Northern blot method, arrays of immobilized complementary DNA (cDNA) and expressed sequence tags have emerged on the heels of... 

As an additional characterization, we hybridize the allele-specific probes to rDNA Southern blots to confirm that they hybridize to restriction fragments containing the region from which they were designed. The Southern blots are hybridized and washed using the same conditions described for RNA slot blots. 

A technique similar to the southern blot. RNA separated by electrophoresis is transferred to a PDVF membrane. Specific RNA sequences are detected... 

Biotechnology is being used in the diagnosis of disease. For example, samples of DNA are treated with restriction endonucleases and then subjected to electrophoresis on gels. Using the Southern blot technique, the x restriction fragments on the gel are hybridized with radioactive cDNA... 

The Northern blot is used to transfer RNA from agarose onto nitrocellulose membranes. Conditions for the transfer are similar to those used in the Southern blot, except for the following. Denaturation prior to transfer is done with methylmercuric... 

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