A transplant is a complex surgical procedure performed to obtain a pearl after about 12 to 18 months. One of the key steps in this procedure is the transfer of the graft (piece of mantle) from the donor oyster. A functional relationship exists between the coating nature of the pearl and the cellular structure of the pearl bag portion of the graft. We have identified two genetic markers of biomineralisation in Pinctada margaritifera, the pearl oyster: Perline and Calcine, responsible for secretion of aragonite and calcite, respectively. After isolating and sequencing a portion of each of these genes, we verified the specificity of these sequences using molecular methods (RT-PCR, in situ hybridisation) and biocomputing methods (alignments, phylogenetic trees, amino-acid composition). We have attempted to make a graft cartography to distinguish zones coding for expression of Perline and Calcine mRNA. The goal of this research is to define precisely the zone for selection of a graft (in a non empiric way) to achieve a desired balance between Perline and Calcine.