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

• Production of the library.
• Screening the bank or library using a radioactive probe(such as cDNA).
• Making probes from proteins.
• Degenerate probes from a sequence.
• Antibody-expressions systems are very successful at finding important genes.
• Finding a needle in a haystack.
  • Ectopic cloning - shuttle vectors w/o origin for one host
• Positional Cloning - A..X..B - Chromosome walking from A to B you will find X.
• You can find any gene that you can observe using mutation. Using transposable elements as gene tags.

EM Southern developed the 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

This web site is provided for instruction in Botany and Zoology 342

by Kenneth G. Wilson,
Professor of Botany
Miami University
wilsonkg@muohio.edu