RT-PCR determination of expression patterns of selected genes potentially related to biomineralization. RT- control reactions prepared from the same RNA were run for all of the PCRs shown here and no contaminating genomic DNA (gDNA) was ever found. For clarity, these RT- control reactions run simultaneously have been cut out here. Positions of molecular weight markers on each side of the gel are shown. The sample identifiers are listed for each lane at the top of the gel (as for Figure 7).