forensic DNA test
concept of allele-specific oligonucleotides
(ASOs) can be extended to
oligonucleotides (SSOs). The DNA sequences of the Cytochrome Oxidase I gene are known for many
species of scallops, including two found in the Northwest
Atlantic, Sea Scallops (Placopecten
magellanicus) and Icelandic Scallops (Chlamys icelandica). The
multiplex test shown here combines an anchor primer for a DNA sequence identical in both species (ScallopR2)
at position 932 with primers specific for either species (PmaCOIF1 and CisCOIF2),
which are differentiated at positions 313 and 473, respectively.
The PCR amplification
product from Placopecten is
thus expected to be 932 - 313 = 619bp in
length, versus a shorter 932 - 473 = 459bp in Chlamys. That is, the size of
the fragment indicates species identity directly.
[HD Marshall, KA Johnstone, & SM Carr
(2007) Forensic Sci Int'l,
"The Case of the
Scurrilous Scallops", a fisherman had a load of
scallops that he claimed were from the open fishery for Icelandic
Enforcement officers suspected they were instead from the closed
fishery for Sea scallops (Placopecten).
proportion of by-catch from the closed fishery might be considered
acceptable, the legal question was: What fraction of the total
catch was from the prohibited species? DNA was extracted from individual scallops and
amplified in the multiplex SSO test
with the three primers. Of the 80 scallops in the test above, all
but eight (blue arrows) show the larger DNA fragment, which indicates
that 90% are Placopecten.
complete series of more than 900 scallops from two vessels, almost
two-thirds were Placopecten.
resulted in conviction and fine.
The multiplex SSO
test provides a rapid, direct means of forensic
identification of large population sample series, without the
necessity of secondary DNA sequencing,
RFLP mapping, or
fingerprinting, and can be adapted to other loci and species.