Biomedical Engineering Reference
In-Depth Information
worn by a bank robber, a cigarette-butt discarded
at the scene of a crime or the back of a stamp on an
envelope used to send a 'poison-pen' or blackmail
letter.
CAD
Anorak Swab
D A C
Historical genetics
Just as multilocus probes have been used for many
applications other than in crime testing, so too have
single-locus probes. A good example is the determina-
tion of the parentage of grapevines used for wine
making. Grapevines are propagated vegetatively, so
that individual vines of a cultivar are genetically
identical to each other and to the single original
seedling from which the cultivar originated. Most of
the cultivars in existence in north-eastern France
are centuries old and their provenance was not
known. However, using 17 microsatellite loci,
Bowers
et al.
(1999) were able to show that 16 of
the common cultivars have genotypes consistent
with their being progeny of a single pair of grape
cultivars that were widespread in the region in the
Middle Ages.
VNTRs can be found in mitochondrial DNA, as
well as nuclear DNA, and these have particular
applications. The reasons for this are threefold. First,
mitochondrial sequences are passed from mother to
child in the egg. Thus, brothers and sisters have
identical mitochondrial DNA. Secondly, the small
size of mitochondrial DNA (16 -20 kb) means that
there is less scope for variability, but this is more
than compensated for by the copy number (~10 000
copies per cell). That is, mitochondrial DNA is
naturally amplified. Thirdly, in very old or degraded
specimens, the nuclear DNA may be totally de-
composed, but mitochondrial DNA can still be
recovered. For example, mitochondrial-DNA ana-
lysis was used to confirm that skeletons found in
Ekaterinburg, Russia, were the remains of the last
tsar and his family (Gill
et al.
1994). A similar ana-
lysis showed that an individual living in Cheddar
Gorge in the UK was related to a Stone Age indi-
vidual whose skull was found nearby. Since bones
are more likely than soft tissue to survive in the
event of major accidents that involve fire, mito-
chondrial DNA analysis will play an increasingly
important role in identifying victims. Indeed, such
an analysis was done in the UK following the 1999
4 kb
Fig. 14.8
Use of a single locus probe to determine the
identity of a rapist. Semen was extracted from an anorak
and a vaginal swab. The victim's profile is in track D and
that of two suspects in tracks A and C. The profile matches
individual A. (Photo courtesy of Dr. P. Gill.)
that it is possible to convert the DNA profile into a
numerical format. This enables a database to be
established and all new profiles can be matched to
that database.
Detection of VNTR polymorphisms requires that
an adequate amount of DNA be present in the test
sample. This is not a problem in paternity disputes
but can be an issue in forensic testing. With the
advent of single-locus probes, the amount of DNA
required is much less of an issue, since the test loci
in the sample can be amplified by PCR. As a result,
it now is possible to type DNA from a face-mask
