Dopa decarboxylase (Ddc) is an enzyme that catalyzes the decarboxylation of L-Dopa to dopamine which is necessary for the synthesis of melanin during an innate immune response in Drosophila melanogaster. Melanization is necessary for wound healing and encapsulation of any foreign agent to prevent infection. Ddc has been identified as a candidate gene involved in lifespan variation by quantitative trait loci (QTL) mapping. Three single nucleotide polymorphisms (SNPs) within this gene have been associated with differences in lifespan. The SNP with the largest effect on lifespan is in the promoter region of this gene, suggesting that this polymorphism may alter the expression of this gene. The primary goal is to develop a quantitative real-time PCR (qPCR) assay for determining Ddc mRNA expression levels in Drosophila melanogaster. Once, optimized, this assay will be used in future studies to determine Ddc mRNA levels among different lines of Drosophila encoding alternative SNPs for Ddc. Eventually, we hope to characterize the degree of association between Ddc expression, SNP variation, as well as variation in immune response and in lifespan.