Physical Location of Products

DNA microarrays on glass slides are usually printed by spotting DNA
solutions from individual wells in the microtiter plates. Each spot on a DNA
microarray uniquely corresponds to the well in a microtiter plate and not to the
identity of a DNA material that has been printed. That is why it is critical to
keep track of the physical location—plate coordinates—of each DNA solution.
In practice, a database user will benefi t from this information at least on two
accounts. First, DNA replicates with the same IDs within the same or different
PCR plates can be easily identifi ed by their different locations on the printing
plates. This facilitates the independent statistical analysis of hybridization data
obtained on the identical DNA sequences. Second, if some nonidentical DNA
sequences demonstrate very similar expression profi les, it is common practice
to verify their relative location on the array. If such genes make a “streak” on
the array (i.e., printed by the same print tip) located next to each other in a
subarray and show identical trend in hybridization outcome (“green” or “red”),
one has to rule out the possibility of cross-contamination during the print. A
similar need arises when one deals with “identical expression profi les” of the
genes that are situated next to each other in a print microtiter plate. Effi cient
recovery of the information about the print plate location of DNA solutions
in question will streamline the analysis as well as help line up the control
experiments.