Many primers have been published based on both mitochondrial
and nuclear genes to trace either bovine or porcine DNA in a variety
of food products. In this experiment, to detect the presence of small
amounts of DNA in gelatin, primers were selected from conserved
regions of mitochondrial genes (cytochrome b). The high copy number
of mitochondrial DNA per cells and the probability of their survival
under different processing conditions ensure amplification of
the expected PCR products even in samples containing small
amounts of DNA (Rodriguez et al., 2004). Furthermore, primerbinding
sites were selected to amplify specific short fragments of
DNA, because of degradation due to gelatin processing.
In the first step, primers were applied to amplify extracted DNA
from gelatin powders with known origin. The gel electrophoresis
results for the PCR amplified products revealed expected bands of
212 and 271 bp for porcine and bovine gelatin, respectively. The
specificity of the method was tested using DNA obtained from gelatin
powders of bovine and porcine origin, against animal meat species
including donkey, sheep, horse, chicken, turkey, and goat, and
no cross contamination was observed (Fig. 1). Tasara et al. (2005)
employed a selection of one bovine and four porcine primer sets,
using conventional PCR, and they showed that the bovine primer
pair was able to detect bovine DNA in gelatin templates specifically.
However, among the four porcine primer sets, only one primer pair
detected target DNA in the gelatin template, but it was nonspecific
and cross-reacted with the bovine DNA template.