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Anonymous
06-04-2004, 09:20 PM
Problem 3: Southern Technique

The "Southern" technique involves:


A. the detection of RNA fragments on membranes by specific radioactive antibodies.
B. the detection of DNA fragments on membranes by a radioactive DNA probe.
C. the detection of proteins on membranes using a radioactive DNA probe.
D. the detection of proteins on membranes using specific radioactive antibodies.
E. the detection of DNA fragments on membranes by specific radioactive antibodies.







Separating DNA by gel electrophoresis

http://www.biology.arizona.edu/molecular_bio/problem_sets/Recombinant_DNA_Technology/graphics/03t.gif http://www.biology.arizona.edu/molecular_bio/problem_sets/Recombinant_DNA_Technology/graphics/03ta.gif


DNA is taken from individuals A and B

It is digested with restriction endonuclease

Fragments are applied onto an Agarose gel for electrophoresis

DNA has a negative charge, and in an electric field migrates towards a positive electrode.

The rate of migration through a gel is proporational to the size of the fragment.



Transfering DNA fragments to nitrocellulose sheets


http://www.biology.arizona.edu/molecular_bio/problem_sets/Recombinant_DNA_Technology/graphics/03tb.gif

DNA fragments are transfered to nitrocellulose sheets where they bind.

DNA fragments are denatured and separated by gel electrophoresis

Fragments are blotted onto a sheet of nitrocellulose and fixed by heating

Blot is reacted with a radioactive probe of RNA or DNA which binds to complementary DNA

Autoradiography is used to detect radioactive fragments


Fixing the fragments of DNA

http://www.biology.arizona.edu/molecular_bio/problem_sets/Recombinant_DNA_Technology/graphics/03tc.gif


The denatures fragments of DNA are fixed by baking.

A radioactive probe is added. It can hybridize with a gene sequence in the DNA.

The sheet is rinsed and placed next to X-ray film for autoradiography.



ans:
B. the detection of DNA fragments on membranes by a radioactive DNA probe.
The Southern technique detects fragments of DNA using a radioactive DNA probe.