CLIN. CHEM.35/9, 1832-1837
(1989)
DNA Fingerprinting
A. H. Cawood
Hypervariable tandem-repetitive minisatellite regions of human DNA can be used to generate individual-specific DNA
fingerprints. Validation studies have demonstrated the reliability of the analysis, the mode of inheritanceof the minisatellites,and the unparalleleddegree of individual specificity. The uses of hypervanable probes in forensic biology,
paternity testing, and the resolution of a wide range of
problemsin genetics,molecularbiology,populationbiology,
and medicineare illustrated.
AddftlonalKeyphrases:
forensicmedicine
gnti
Genetic polymorphisms
detected by protein variants
have been used extensively in identity and relationship
testing, and as marker systems for linkage analysis. The
power of this indirect detection is limited by the amount of
variability in the systems, and by the instability of some of
the protein markers in dried stains (e.g.).
The amount of variability
is limited because the systems
are constrained
by the fact that expressed sequences of
DNA are being studied. Too much change in such sequences would cause a failure in the production of the
particular
protein, or would lead to the production of a
protein altered to such an extent that it could not function.
Selection against defective proteins reduces the amount of
variability
in the population.
Direct analysis of DNA has revealed extremely polymorphic areas of the genome. Free of the constraints
imposed
upon variability within the expressed region of the genome,
parts of the nonexpressed
sequences have been discovered
that have hundreds of variants.
The first of these hypervariable
regions (HVRs) was
identified in 1980 (1), although the structural
basis for the
observed variability
was not known at the time.1 Subsequently, many other HVRa were identified, and it became
clear that families of HVRa are thspersed throughout
the
genome (2, 3). The number of HVRs in the genome is
unknown, but evidence suggests that there are more than
1500 (3).
Analysis of HVRs is now having a major impact in
forensic investigations
and paternity
analysis, giving dramatic increases in discrimination
compared
with analysis
for protein polymorphisms.
HVRs are also being used to
study a wide variety of problems in population biology,
cancer monitoring,
animal pedigree
analysis,
and linkage
studies.
Features of HVRs and their applications
are illustrated
here by the group of HYRs discovered
by Jeifreys et al. (2,
4).
ICI Diagnostics,
20874.
20271 Goldenrod Lane, Germantown,
CLINICALCHEMISTRY,Vol. 35, No. 9, 1989
A 33-bp (base pair) repeat sequence, repeated four times
in tandem, is found within the human myoglobin gene
By using several copies of this repeat, joined end to end, to
screen human DNA, Jeffreys et al. (2) discovered that many
sites in the DNA contained similar sequences. Isolation of
some of these newly detected loci and screening of human
DNA with them revealed complex patterns of hypervariable bands. The parts of the DNA detected, called minisatellites, were found to share a consensus, or core, sequence
repeat.
All of the minisatellite
loci detected
thus far consist of
tandem repeats of sequences that differ from one locus to
another, but all show homology to the core sequence. The
extreme degree of polymorphism
observed
at these boci
arises from variation in the number of times the minisatellite sequence is repeated.
This type of hypervariable
region is also known as a VNTR (variable
number of
tandem repeats). Two sequences in the group, 33.6 and
33.15, have different
variants
of the core sequence,
and
detect distinct subsets of minisatellite
loci.
An example of the kind of pattern generated by using
these VNTR probes is shown in Figure la. The method
used to produce these multilocus
patterns
is described
later.
Several of the loci detected by the multilocus probes have
been isolated, cloned, and characterized
(4, 6). These parts
of the DNA can be used to reveal the length variants at the
specific locus, and only that locus, in the DNA from any
individual. With these locus-specific,
or single-locus probes,
(5).
SLP
mcf
I
-
-
I
-
-
-
-
MD
‘Nonstandard
abbreviations: HVR, hypervariable
region;
VNTR, variable number of tandem repeats; HLA, human leukocyte antigen; and RFLP, restriction fragment length polymorphism.
Received April 13, 1989; accepted June 5, 1989.
1832
Types of HVR Probes
a
b
C
Fig. 1. Analysisof hypervanable regions in DNA froma mother
(m)-child (c)-father (I) trio: (a) muftilocus
pattern,(b) locus-specific
probe ‘cocktail,”(c) singlelocus-specificprobe
only
whether
one or two bands
the individual
are
revealed,
depending
upon
is homozygous
or heterozygous
for a
of tandem repeats
at that locus. The
particular
number
extent of the length polymorphism at these loci is such that
>95% of individuals inherit different numbers of repeats
from each of their parents and thus exhibit two bands
(Figure lc).
Locus-specific probes can be combined to reveal the
length polymorphisms at several loci simultaneously
(Figure lb). The pattern
of hypervariable
bands produced
displays
a complexity
intermediate
between that produced
by the multilocus probes (Figure la) and a single locusspecific probe (Figure lc).
The patterns of bands seen in Figure 1 reveal the lengths
of core-containing
sequences at one locus, several loci, or
many loci in DNA from three individuals.
Before the
analysis
of these patterns
could be applied to specific
problems, the constancy and reproducibility
of the patterns, their individual specificity, their mode of inheritance, and their performance relative to traditional analyses had to be determined.
Constancyand Reproducibility
DNA has been examined from various sources (Figure 2).
The patterns of bands in DNA from an individual are the
same whatever the source. The band pattern shown in
Figure 2 was produced
by using a mixture of four locusspecific probes, but the patterns produced with multilocus
probes or individual locus-specific probes similarly show no
change with source of DNA. There is no difference in
pattern between fresh, frozen, or dried materials, and the
material
upon which a blood or semen stain is found makes
no difference to the pattern, although in terms of recovery
of DNA, some substrates are more difficult to handle than
others.2
Extensive
comparisons
have been performed between
band patterns produced by different researchers
with DNA
from the same individuals.
In one study (7), DNA analyses
were performed on over 700 different blood samples, each of
which was analyzed by between two and four researchers.
i
2
data from researchers
3
4
5
6
at ICI; see acknowledg-
7
8
9
10
Fig. 2. Constancy of band patterns after analysis of DNA from
severalsources from one individual:1, blood; 2, semen; 3, cellsfrom
saliva; 4, cellsfrom urine; 5, head hair roots;6, pubichair roots;7,
eyebrowhair roots; 8, buccalswab; 9, semen stain;and 10, blood
stain
Inheritance of the Patterns
Examination
of the patterns of bands in the DNA from
pedigrees
and proven
mother-childfather trios has shown that bands are inherited in a simple
mendelian
fashion, and behave
as co-dominants;
i.e., both
the maternally
and paternally derived variants at any
given locus are detectable:
the presence of one does not
mask the presence of the other. For the multilocus band
pattern, there is no evidence of any significant deviation
from independent assortment of bands or of X-linkage2(2,
extensive
PropertIes of Mlnlsatelllte Probes
2Unpublished
ments.
There were no differences between the patterns produced
by different researchers with any of the bloods analyzed.
Constant patterns are also produced when DNA is analyzed after extraction
from the same subject at different
times. Blood drawn from one individual at various times
over the past three years has been subjected to DNA
fingerprint
analysis
with multilocus
and locus-specific
probes >3000 times by >50 researchers at three laboratories in the U.K. and U.S., with no evidence of any changes
in the patterns.
known
8).
The chromosomal locations of the locus-specific probes
are known (4), and variants at any one locus are inherited
independently
of variants at the other loci. This is to be
expected, given that the bands detected by the locusspecific probes are a subset of the bands detected by the
multilocus probes, which themselves
show no significant
deviation from independent assortment.
Individual Specificity
For any given locus, the frequency of individuals possessing a particular combination of variants can be estimated
by the Hardy-Weinberg
theory, given that the frequency of
gametes containing any given variant is known (see 9). The
theory predicts that the frequency of individuals heterozygous for two variants, or alleles, with gametic frequencies
of p and q, will be 2 pq, and that homozygotes,
i.e.,
individuals
with two identical variants,
would have frequencies of p2 and q2.
The variants detected are pieces of DNA that differ from
one another in the number of tandem repeats of a sequence
at a particular locus. The differing lengths of DNA can be
estimated
from measuring
their migration
after electrophoresis through an agarose gel, and by comparing this
migration with that of DNA fragments of known size (10).
The frequencies of alleles have been determined in populations of U.K. Caucasians2
(6), U.K. Afro-Carribeans,
Bangladeshis,2
and U.S. Caucasians,
blacks, Hispanics,
and orientals2 (11). The resolution of different alleles is a
feature of the conditions of electrophoresis used and is less
precise than the size of a single repeated sequence for any
of the locus-specific probes studied. Thus the true extent of
polymorphism is almost certainly
underestimated.
The mean probability of a chance match between the
genotypes of two randomly chosen individuals ranges from
0.0002 to 0.0003 for the locus-specific probes msl, ms3l,
ms43, and g3 (4). Because these loci are independent of one
another, the cumulative
probability
of a chance match is
theoretically
the product of the individual probabilities. In
practice, the probabilities depend upon the actual population frequencies
of the alleles in the test material.
The
more often the observed alleles occur in the population, the
greater wifi be the likelihood of a chance match.
Assessment of the individual specificity of the multilocus
CLINICALCHEMISTRY,Vol. 35, No. 9, 1989
1833
band patterns, known as “DNA fingerprints,” is based on
the probability that two unrelated individuals share a band
at the same position. Jeffleys and co-workers (12) found
that the amount of band sharing was related to the size of
the alleles, with larger alleles being shared less often than
smaller ones. Overall, for the range of scorable (i.e., reliably detectable) bands (from about 3 kb), the probability of
band sharing for probes 33.6 and 33.15 is not more than
0.25 in populations in the U.K.2 (12), continental
Europe
(12, 13), the U.S. (7), and Japan (14). The probability of a
chance match of multilocus
DNA fingerprints
from two
unrelated individuals chosen at random is estimated conservatively by 0.25”, where n is the number of bands in the
pattern. The average number of bands observed in the
scored region of the 33.6 and 33.15 patterns is 35, giving a
mean probability of a chance match of 8.5 x 10
or 1 in
1021. Given that the current
world population is approximately 5 x iOn, we can consider the multilocus
DNA
fingerprint to be unique to an individual. The one exception
to this individual
specificity is monozygotic twins: they
have identical genotypes, and thus identical DNA fingerprints.
Comparison with Other Methods
DNA fingerprinting
analysis
has been performed
on 219
trios from the U.S., for which
paternity testing had also been carried out with “red cell”
antigens,
“red cell” enzyme systems, human leukocyte
antigens
(HLAs), and serum protein systems (15, 16). The
DNA testing results supported the results obtained by the
traditional
methods, and could resolve previously inconclusive results. A similar comparison, performed by the National Public Health Institute
in Finland (13), demonstrated that even when HLA typing could not discriminate
between putative fathers, the results of the DNA fingerprint analysis were unambiguous.
mother-child--(alleged)father
Eflects of Sample Storage Conditions
Liquid blood stabilized with EDTA as an anticoagulant
provides high-Mr DNA for several years after storage at
-70 #{176}C.
Storage at temperatures
>37 #{176}C
reduces the useful
life of the sample to weeks-or
days for temperatures
as
high as 56#{176}C.
The key factor affecting recovery of intact
DNA from stains and samples such as hair roots is moisture. If samples are stored in conditions of high humidity,
degradation
of the DNA occurs in days (semen stains) or
hours (hair roots), even at 4 oC2 Rates of degradation in
moist samples are accelerated at higher temperatures.
However, high-Mi DNA can be recovered from dried or
frozen material
after several years (17, 18; and unpublished casework experience). The stability of DNA is an
important feature in the analysis of forensic samples, and
simple precautions
applied to sample storage, such as
keeping samples dry or frozen or stabilizing
with EDTA,
can ensure that the unique discriminatory
power of DNA
analysis can be used in a wide variety of investigations.
Importantly,
in all instances examined to date, when the
DNA degrades, the fingerprinting
bands, whether multilocus or locus-specific, become progressively more difficult
to detect. However, there has been no example of the
generation of new bands after either degradation
during
storage or deliberate degradation with deoxyribonuclease
I
(M. B. T. Webb, personal communication).
Thus, the effect
of extreme degradation is the loss of information, not false
incrimination.
1834
CLINICALCHEMISTRY,Vol. 35, No. 9, 1989
Sensitivity
About 500 ng of high-Me DNA is required for the production of a full multilocus DNA fingerprint pattern2 (18). The
detection limit of the locus-specific probes is much lower.
As little as 30 ng of high-Me DNA can yield a signal, which
allows analysis of as little as 1 L of blood or semen, or a
single hair root. This sensitivity
means that, although
multilocus
probes give the best individual discrimination,
locus-specific probes are of more general use in forensic
investigations.
A further advantage
of the locus-specific probes is their
ability to resolve samples of mixed origin. Although it is
possible to extract DNA preferentially
from spermatozoa,
in a mixture of semen and blood, for example (18), the
differential lysis technique does not always work, and in
some casework is not desirable for evidential reasons.
Multilocus
patterns
are often too complex for reliable
resolution of DNA from more than one individual, but
locus-specific probes give unparalleled
resolution
of mixtures. Figure 3 shows the bands revealed in DNA obtained
from two individuals, and mixed in various proportions.
Alleles from the second individual were detectable when
present in as little as 0.5% of the DNA mixture. Therefore,
mixtures
of DNA from several individuals,
and from a
variety of sources, can be analyzed, which has been invaluable in the investigation of multiple rapes.
General DescrIptIon of Methods
DNA is extracted with protease K and sodium dodecyl
sulfate, purified by using phenollchloroform
followed by
ethanol precipitation,
and digested with the restriction
endonuclease
Hinfl. After electrophoresis
through
0.7%
agarose, the DNA is transferred
to a nylon membrane by
capillary
blotting. The VNTR sequences
are detected with
probes labeled with 32P.
For isolating DNA from spermatozoa, dithiothreitol
is
added to break the disulfide bridges in the protein coat of
the sperm head. Dithiothreitol
also improves the yield of
DNA from blood clots. Improved yields from dried stains
can be obtained by washing with isotonic saline containing
EDTA, 10 mmol/L, before lysis.
Analyzable
DNA can be recovered from blood, dried
bloodstains,
semen, dried seminal fluid stains (including
semen on vaginal swabs), bone marrow, hair root cells,
buccal swabs, cells from saliva (0.5 mL is ample), and urine
(50 mL yields enough DNA for autoradiographic exposures
of <48 h), bone, fetal tissue, and post-mortem samples
(skeletal muscle is particularly good).
Fig.3. Analysis of DNAfrommixed blood samples
Blood from two brothers, AT-3 and AT-4, were mixed to givethe following
volume proportions of AT-4: lane 1, 5%; 2, 2.5%; 3. 1.25%; 4,0.7%; 5, 0.5%;
6,0.3%; 7, 0.2%; 8, 0.05%; 9,0% (AT-3alone);10, 100% AT-4
ApplIcatIons
Clearly, direct detection of the variability
at sites of
tandem repetition of short sequences in the genome affords
previously unattainable
levels of discrimination
in identification. The tandem repeats are inherited simply, and the
methods used for their detection are robust and sensitive.
How, then, is this technology used practically?
PaternityTesting
The primary use of the multilocus-probe
DNA fingerprinting has been in paternity testing. The amount of DNA
is rarely limiting in such tests, so the superior individual
specificity
of the multilocus probes can be used.
In a paternity
test, digested DNAS from the mother,
child, and putative father or fathers are processed side by
side. The pattern of bands revealed in the child’s DNA is
compared with that in the mother’s DNA. All bands that
match in position and relative intensity are, or could be,
maternal in origin. Thus all of the remaining bands in the
DNA fingerprint
of the child must have been inherited
from the biological father. If all of these bands are present
in the DNA fingerprint
of the alleged father, this is evidence of paternity. The strength of this evidence is orders of
magnitude
greater than can be achieved by using protein
polymorphisms, or even HLA typing (13, 15, 16).
An example from casework in the U.K. is illustrated
in
Figure 4a. A man was charged with the rape ofan 11year-old girl, who as a result of the rape has given birth to
a live baby. Blood was taken from the man, the girl, and the
baby. A comparison
of the DNA fingerprints
produced
by
using the multilocus probes 33.6 and 33.15 revealed the
presence of 14 bands in the child’s pattern, which were not
found in the mother’s pattern. All 14 of these bands were
matched by bands in the DNA fingerprint of the defendant.
The probability that all of these paternally
derived bands
would match by chance alone was 0.25’s =
x iO or 1
in 268 million. The defendant pleaded not guilty, and the
DNA evidence was presented to the court. The man was
convicted at the Central Criminal Court, Old Bailey, and
was sentenced to 7.5 years imprisonment.
In a small proportion of analyses, a band appears in the
DNA fingerprinting
of a child that does not match any band
in either mother or father. In established
pedigrees, this
Identification in Forensic Examinations
An example of the exclusion of suspects from a murder
investigation
by the multilocus DNA fingerprint
is shown
in Figure 5. A drainage sample of seminal fluid was taken
from the body of a woman who had been dead for approximately two days. DNA was extracted from the spermatozoa
after differential lysis to remove DNA from any containinating cells from the victim. DNA was also extracted from
blood taken from the victim’s body. Comparison of the DNA
C
S2.V
1
.1
jE
MCAF
-.
must arise through
mutation.
The frequency
with which
mutation produces unmatched
bands has been determined
by observation (2,12), and knowledge of the mutation rate
can be used to calculate the relative likelihood of mutation
vs the chance of matching all but one of the nonmaternal
bands.
Figure 4b shows an example of an unmatched
band. The
“child” pattern was produced from DNA extracted from a
chorionic
villus biopsy; 23 bands were nonmaternal,
22 of
which matched bands in the putative father. The relative
likelihood of a mutation rather than a chance match of 22
of 23 bands was one in 2 x 1011. The relative likelihood of
a mutation rather than a chance match of 22 of 23 bands, if
the putative father was a first-degree
relative of the true
father, was one in 662. Because the man’s relatives
could be
excluded from paternity anyway, it was clear that the man
tested was the true father. The particular
interest of this
analysis was that the father had classical nonmosaic tnsomy 21 Down Syndrome, a condition previously thought to
be associated with total infertility in males.
Relationship
testing with these hypervariable
probes is
not limited to complete families. The resolution of relationships has been possible even in complex cases where no
putative father was available, for example, when it was
necessary to determine whether a boy was the son or the
nephew of the woman wishing to bring the child into the
U.K. (19), or when paternity needed to be established years
after the putative father had been killed in an automobile
accident (20).
.
r
-
a,
--‘
a
Fig. 4. Paternity testing with multilocus probe 33.15: (a) criminal
paternity(M, mother; C, child; AF, alleged father) and (b) mutation
producingan unassignedband (arrov, in the DNA fingerprintof a
child(M, mother;F, father;C, child)
Fig. 5. Exclusion of suspects by use of multilocusprobe3.15
C, control DNA; E, DNA from semen found on victims body; V. DNA from
post-mortem blood sample from victim; SI, 82, DNA from suspects
CLINICALCHEMISTRY,Vol. 35, No. 9, 1989
1835
fingerprints
indicated that the DNA from the spermatozoa
was not contaminated
by DNA from the victim. Two
suspects were arrested on the basis of their previous criminal records and strong circumstantial evidence. Comparison of their DNA fingerprints proved that neither man was
the source of the seminal fluid taken from the body. The
police were able to continue their investigation and apprehended a man whose DNA fingerprint matched that of the
seminal fluid. The suspect is awaiting trial.
Although
multilocus probes can be used in some determinations
of the identity of the source of body fluids, the
usually limited amount of material available and the potential complication caused by mixed origin of samples make
the locus-specific probes more widely applicable in forensic
examinRtons.
A recent case in the U.S. illustrates the power
of locus-specific DNA analysis. A girl was sexually assaulted
while anesthetized for surgery. A gauze wipe of a tube taken
from the victim’s mouth was found to contain spermatozoa.
DNA was extracted from the swab in a two-stage process. In
the first stage, treatment
with protease K and sodium
dodecyl sulfate released DNA from any cells present that
were not spermatozoa. The pattern of bands revealed within
this DNA (Figure 6, lane 2) matched that in the DNA
extracted from blood from the victim. The second part of the
extraction used included protease K, sodium dodecyl sulfate,
and dithiothreitol
to release DNA from the spermatozoa.
The pattern of bands revealed in this extract (lane 3)
matched the pattern in the DNA from the suspect.
The patterns in Figure 6 were produced with a “cocktail”
of locus-specific probes. By subsequent re-hybridization
with the individual probes, all bands were assigned to
specific loci. This allowed calculation of the frequency of the
observed combination of characters in the population. The
calculated frequency was one in 4.7 X iO. At the trial, the
judge ruled that the DNA evidence was admissible. The
defendant was found guilty.
11”
Fig. 6. Use of locus-specific probes in forensic analysis
1,DNA from vIctim; 2, DNA from first lysisof extract from gauze wipe; 3, DNA
from second lysisofextractfrom gauze wipe; 4,DNA from suspect
1836
CLINICALCHEMISTRY,Vol. 35, No. 9, 1989
Another application of DNA testing in cases with potential legal impact is the fingerprinting
of high-Mr DNA
extracted
from cells in urine. Such testing will permit
unequivocal resolution of the origin of urine samples that
have given positive results in drug testing.
Other Applications
Linkage analysts.
Advances in our understanding
of
inherited diseases for which the biochemical
basis of the
disorder is not yet understood are coming through isolation
of the affected loci, characterization
of the primary genetic
defect, and subsequent elucidation of the biochemistry
and
physiology of the disorders. This “reverse genetics” depends
upon precise mapping of the affected locus in the DNA.
Unless a disorder is commonly associated with a particular
chromosomal
abnormality, which can narrow down the
target area, mapping has to rely upon the chance cosegregation of the disease and variants of loci of known
position. Analysis of restriction fragment length polymorphisms (RFLPs) has greatly aided the search for co-segregating markers. However, most RFLPs are dimorphic and
can have heterozygosities
of not more than 50%; indeed,
many RFLPs have heterozygosities
much less than this.
Moreover, in any family group, at least one of the parents
of affected offspring has to be heterozygous
at the loci for
both the disease and the marker; this makes many families
totally uninformative.
The very high heterozygosities
associated with VNTR loci make them exceptionally promising as markers that will greatly increase the likelihood of
any family being informative. In addition, the ability to
detect many loci simultaneously
by using the multilocus
probes holds the potential for speedier detection of linked
markers than has been possible so far.
A further use of VNTR analysis in this context is the
demonstration
of the true relationships
within family
groups. In a recent investigation
of an unusual case of
thalassemia,
in which the mother was heterozygous but the
claimed father was homozygous
for the normal alleles,
DNA fingerprinting
was used to determine the true relationship. The DNA analysis revealed that the mother’s
brother was the true father, thus explaining the apparently
anomalous genotype of the child. Such determinations
have
important consequences for genetic counseling (21).
Investigations
of the relative contributions of heredity
and environment to a variety of human traits involving
studies of twins can also be helped by VNTRs (13), by
establishing
whether a set of twins is monozygotic or
dizygotic.
Medical practice. The extremely high individual
specificity of VNTR probes allows their use in monitoring bonemarrow transplantation,
even when donor and recipient are
closely related (22). In another application,
VNTR probes
can be used to monitor certain types of neoplasia, which
involve genomic rearrangements
and clonal proliferation.
Changes in the multilocus DNA fingerprint that involve the
loss of bands or the production of novel bands have been
observed in gastrointestinal
cancer (23, 24). Study of such
changes will be useful in the assessment of the clonal origins
of and genomic changes in these types of cancer. Similar
changes have been observed between remission
and relapse
in acute lymphoblastic
leukemia. Preliminary
studies suggest that DNA fingerprinting
may provide a more sensitive
monitoring
of residual disease than the cytological and
cytogenetic analyses currently in use (25).
Cell line authentication.
Much current
biological re-
search involves use of specific cell lines. The value of the
results of most of the research depends upon accurate
identification
of the lines being studied. For example,
experiments investigating
the steps involved in induction
of neoplastic changes would be valueless if the observed
transformations
were caused not by the experimental
treatment
but by contamination
of the line. Such contamination is quite common, as is simple mis-identification
of
lines (26). DNA fingerprinting
can verify whether or not
cross-contamination
has occurred, e.g., in a study of cellular transformation
in human keratinocytes
(27).
Nor is this analysis restricted
to human cell lines. A
recent study (28) compared CHO and V79 lines derived
from the Chinese hamster,
and demonstrated
the use of
DNA fingerprinting in identifying fusion hybrids without
having to manipulate
other markers into the system.
Animal
studies. The multilocus probes detect VNTR
polymorphisms
in a wide range of animals. Pedigree and
linkage analysis in dogs and cats (29), population studies of
wild sparrows (30), investigations
of behavior and breeding
success in dunnocks (31), and studies of inbred strains of
mice (32) have all benefited from DNA fingerprint analysis.
The individual specificity of the band patterns should also
help in the study of the migration and breeding success of
(e.g.) whale populations.
A harpoon-biopsy
can provide
enough DNA for fingerprinting
and remove the need to
physically tag the animals (33).
To conclude: the discovery of this extreme polymorphism
in DNA, and the elucidation of the basis of it, have provided
the means to solve problems in a range of fields of biological
research.
Communication
between scientists in different
specialties will doubtless broaden the use of hypervariable
probes. Those interested in keeping informed of the applications of the technique will find invaluable
a newsletter
from the Department
of Genetics, University of Cambridge,
U.K. (34).
This technology is the subject of various granted patents
and patent applications. All commercial enquiries should
be directed to ICI Diagnostics,
Gadbrook Park, Rudheath,
Northwich, Cheshire, CW9 7RA, U.K.
I am indebted to the following colleagues within IC! who allowed
mete quote their work: J. C. Smith, B. Hopkins (IC! Diagnostics);
D. D. Garner, R. W. Cotton (Celimark Diagnostics, U.S.A.); P. G.
Debenham, M. B. T. Webb (Cellmark Diagnostics, U.K.).
References
1. Wyman A, White R. A highly polymorphic locus in human
DNA. Proc Natl Acad Sci USA 1980;77:6754-8.
2. Jeeys
AJ, Wilson V, Them SL. Hypervariable “minisatellite”
regions in human DNA. Nature (London) 1985;314:67-73.
3. Nakamura Y, Leppert M, O’Connell P, et al. Variable number
of tandem repeat (VNTR) markers for human gene mapping.
Science 1987;235:1616-22.
4. Wong Z, Wilson V, Patel I, Povey S, Jeffieys AJ. Characterization of a panel of highly variable minisatellites cloned from human
DNA. Ann Hum Genet 1987;51:269-88.
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CLINICALCHEMISTRY,Vol. 35, No. 9, 1989
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