Colony Hybridization @biogeny net
A method has been developed whereby a very large number of colonies of Escherichia coli carrying different hybrid plasmids can be rapidly screened to determine which hybrid plasmids contain a specified DNA sequence or genes. The colonies to be screened are formed on nitrocellulose filters, and, after a reference set of these colonies has been prepared by replica plating, are lysed and their DNA is denatured and fixed to the filter in situ. The resulting DNA-prints of the colonies are then hybridized to a radioactive RNA that defines the sequence or gene of interest, and the result of this hybridization is assayed by auto-radiography. Colonies whose DNA-prints exhibit hybridization can then be picked from the reference plate.