Each filter is labelled at the top left hand corner (Mouse BAC 1, Mouse BAC 2 ..........Mouse BAC 10). This label serves as an orientation mark. The 10 enclosed tables provide detailed information about the layout of clones on each of 10 filters.

The first table shows a typical 22 x 22 cm membrane with 36,864 spotted clones. Each filter is divided into 6 panels (indicated by 1, 2......6). The panels are numbered from left to right and eight 384-well plates are gridded, in duplicate, in each panel. Within each panel, numbers 1-24 correspond to the 24 columns and letters A-P are the 16 rows of the eight 384-well plates in the panel. Each dot represents a clone from a single microtitre plate well. A group of 16 dots corresponds to a 4x4 array of duplicate clones from the 8 microtitre plates (8 x 2). Thus each panel consists of 6144 clones (384 x 8 x 2). The next set of 10 tables shows the order of the 8 plates (in duplicate) within each panel of filters Mouse BAC 1 and Mouse BAC 2. Panel 1 ( contains plates 1-8, 2 contains 9-16 and so on. This plate order has been maintained on all the membranes, e.g.

In our experience the interpretation of filters is easier if some background radioactivity is left on the filters. The autoradiographs will then clearly define the 4x4 pattern and the relative position of the positives against this pattern.

The interpretation of positive signal(s) can be done by following the procedure given below:

1. Identify the membrane on which the positive signal is located (in duplicate).

2. Use the label position to orientate the filter and identify the panel in which the positive clones are located.

3. Work out the microtitre co-ordinates of the 4 x 4 array by referring to the row (A-P) and column (1-24) designations.

4. Within the identified 4 x 4 array determine which plate number contains the positive clone.

Check that any two signals fall in one of the following patterns:

5. Record the identity of putative positives by following the convention PLATE-ROW and COLUMN (e.g. 164-L15).

The sheet also allows for an alternative method of interpretation