what is the difference between a northern and southern blot?

Answer 1

Southern blot is for DNA and Northern is for RNA

Answer 2

The western blot (sometimes called the protein immunoblot) is a widely used analytical technique used to detect specific proteins in a sample of tissue homogenate or extract. It uses gel electrophoresis to separate native proteins by 3-D structure or denatured proteins by the length of the polypeptide. The proteins are then transferred to a membrane (typically nitrocellulose or PVDF), where they are stained with antibodies specific to the target protein The eastern blot is a biochemical technique used to analyze protein post translational modifications (PTM) such as lipids, phosphomoieties and glycoconjugates. It is most often used to detect carbohydrate epitopes. Thus, Eastern blotting can be considered an extension of the biochemical technique of Western blotting. Multiple techniques have been described by the term Eastern blotting, most use proteins blotted from SDS-PAGE gel on to a PVDF or nitrocellulose membrane. Transferred proteins are analyzed for post-translational modifications using probes that may detect lipids, carbohydrate, phosphorylation or any other protein modification. Eastern blotting should be used to refer to methods that detect their targets through specific interaction of the PTM and the probe, distinguishing them from a standard Far-western blot. In principle, Eastern blotting is similar to lectin blotting (i.e. detection of carbohydrate epitopes on proteins or lipids) he northern blot is a technique used in molecular biology research to study gene expression by detection of RNA (or isolated mRNA) in a sample. A Southern blot is a method used in molecular biology for detection of a specific DNA sequence in DNA samples. Southern blotting combines transfer of electrophoresis-separated DNA fragments to a filter membrane and subsequent fragment detection by probe hybridization.

Answer 3

Southern Blot (Fig B.27)

* Used for determining the presence of a particular sequence of DNA in a mix (as long as it hybridizes to probe).
* genomic DNA (gDNA) digested with a restriction enzyme results in production of many DNA fragments of differing size. When fractionated by electrophoresis, results in a smear.
* fractionated DNA in gel denatured with NaOH to separate DNA strands (to hybridize with probe later)
* DNA in gel transferred to nylon membrane and covalently cross-linked. Pattern on gel same as pattern on membrane.
* membrane bathed in solution containing radiolabeled probe.
* Probe will hybridize to homologous fragments.
* Membrane washed to remove nonspecific binding of probe.
* membrane exposed to film. Film developed (autoradiogram)
* DNA fragments in membrane which hybridized to probe will show up on film as dark bands. Size of these bands calculated from size markers.

Northen Blot

* Same as southern blot, except its RNA that is being fractionated in gel
* Used to determine when, where, and by how much genes are expressed.
o example: if RNA extracted form different tissues (including pancreas), fractionated on a gel, transferred to membrane and then probed with insulin gene, it should only hybridize to mRNA molecules of the same size only in the lane loaded with pancreas total RNA.

Western Blot

* Involves separation of proteins in gel, transfer onto membrane, then probe with antibody.
* Used to detect specific proteins in a sample