blue-white screen

A screening technique for the rapid detection of recombinant bacteria in vector-based molecular cloning experiments. DNA of interest is ligated into a vector, which is then inserted into a host cell; these are grown in the presence of X-gal. Cells transformed with vectors containing recombinant DNA will produce white colonies; cells transformed with non-recombinant plasmids (i.e. only the vector) grow into blue colonies.