How to find clones from a genomic library or gene bank?

• Production of a library using lambda or Charon phage.
• Screening the bank or library using a radioactive probe(such as cDNA) ie Sourthern Hybridization.
• Finding a needle in a haystack.
• Positional Cloning - A..X..B - Chromosome walking from A to B you will find X.
• Making probes from proteins.
• Degenerate probes from a sequence.
• Antibody-expressions systems are very successful at finding important genes.

Gene mutation to find genes

• You can find any gene that you can observe using mutation. Using transposable elements as gene tags.

Review of EM Southern's proceedure for finding genes in digests of DNA. It was modified and has become one of the most widely known techniques.

• Separate the digested or restricted DNA on an agarose gel using electrophoresis.
• Prepare a membrane replica of the gel by transferring the separated DNA to nylon membrane, hybridize with known probe and develop
• Autoradogram. Similarly you can detect for RNA (Northern Blot). You can detect proteins using antibodies (Western Blot).
• Results of a Southern Blot
• Comparison of a Northern and Southern Blot or hybridization