An improved differential screening protocol that allows the detection of marginally induced or repressed mRNAs.

摘要

The invention differential screening technique, single plate one transfer (SPOT), which allows for the sensitive and reliable detection of mRNAs induced or repressed only 2 to 3 fold or less with respect to background. The basis for this technique is to symmetrically spot in quadruplicate or more on a single plate, a large number of potentially positive plaques obtained from a primary, conventional screen. Only one lift is made from this plate in order that there will be minimal variability in DNA transfer. This filter is cut into symmetrical sections such that DNA from all plaques are multiply represented on each section. The sections are next hybridized with different probes. Since each section contains an approximately identical amount of DNA per plaque, one may accurately detect mRNAs that are induced or repressed only slightly above background.