Eurofins | contact us | careers | FAQ

Restriction Fragment Length Polymorphism (RFLP)
RFLP was one of the original applications of DNA analysis for forensic investigation. A sample of DNA would be digested using a special enzyme, known as a restriction endonuclease.
This would cut the DNA at a specific sequence pattern know as a restriction endonuclease recognition site. The presence or absence of certain recognition sites within a DNA sample would generate variable lengths of DNA fragments, which were separated using gel electrophoresis. They are then hybridized with DNA probes that bind to a complementary DNA sequence in the sample.
In order to utilise RFLP relatively large amounts of DNA is required. In addition, samples degraded by environmental factors, such as dirt or mould, do not work well with RFLP which, has led to the development of newer, more efficient techniques for DNA-analysis.

[back to top]

Polymerase Chain Reaction (PCR)
Analysis PCR is the process by which millions of exact copies of DNA from a biological sample can be produced. The DNA amplification with PCR allows DNA analysis on biological samples as small as a few skin cells, the ability of PCR to amplify such tiny quantities of DNA enables even highly degraded samples to be analyzed. Great care, however, must be taken to prevent contamination with other biological materials during the identifying, collecting, and preserving of a sample.

[back to top]

STR Analysis
Short tandem repeat (STR) technology is used to evaluate specific regions (loci) within nuclear DNA. Variability in STR regions can be used to distinguish one DNA profile from another. The United Kingdom and European Union uses a standard set of 13 specific STR regions for SGM+. SGM+ is a software program that operates national databases of DNA profiles from convicted offenders, unsolved crime scene evidence, and missing persons.
The odds that two individuals will have the same 13-loci DNA profile are about one in one billion.

[back to top]

Mitochondrial DNA Analysis
Mitochondrial DNA analysis (mtDNA) can be used to examine the DNA from samples that cannot be analysed by RFLP or STR. Nuclear DNA must be extracted from samples for use in RFLP, PCR, and STR; however, mtDNA analysis uses DNA extracted from another cellular organelle called a mitochondrion. While older biological samples that lack nucleated cellular material, such as hair, bones, and teeth, can be analysed with mtDNA. mtDNA has a matrilinear mode of inheritance and can show whether two or more individuals share a common maternal ancestor. In the investigation of cases that have gone unsolved for many years or in missing person or mass disaster investigations, comparing the mtDNA profile of unidentified remains with the profile of a potential maternal relative can be an important technique.

[back to top]

Y-Chromosome Analysis
The Y chromosome is passed directly from father to son, so the analysis of genetic markers on the Y chromosome is especially useful for tracing relationships among males or for analyzing biological evidence involving multiple male contributors. In sexual assault cases, the biological samples recovered are often a mixture of male and female DNA, which can present certain problems with result interpretation. As the Y-chromosome is exclusively in men, a Y- chromosome test allows profiling of the perpetrator without analysing DNA from the victim.

[back to top]

Parentage and Relationship Testing
Parentage testing is used to determine whether and alleged individual is the biological parent of a child. In legal practice parentage testing is extensively used in immigration cases, child support cases and in situations when the birth certificate has to be amended to include or change a parent. The parentage report contains two pieces of information required for interpretation of the data.
The Combined Parentage index (CPI)
Indicates how many times the alleged parent is more likely to be the biological parent of the child as opposed to another individual. For example, a CPI of 15,000 indicates that the alleged parent is 15,000 times more likely to be the true parent of the child than another individual. The Probability of Parentage
Is the probability that the alleged parent is the biological parent of the child. This statistic, expressed as a percentage, is an alternative interpretation of the CPI.
Parentage testing can be conducted both prenatally (predominantly paternity) and postnatally (paternity and maternity). DNA samples are routinely collected by mouth swab however; blood, hair or pathology tissue samples can also be used. Commonly 16 genetic markers are looked at, achieving a probability of parentage of more than 99.99%.

[back to top]

Relationship Testing
Individuals that are related will have inherited identical genetic markers from a common ancestor as opposed to the markers being inherited by unrelated individuals. Among the most commonly used relationship tests are; siblingship test (determines whether tow individuals have one or both parents in common), avuncular test (determines whether an individual is an uncle/aunt to another individual), grand parentage test (determines whether an individual is a grand parent to another individual), cousinship test (determines whether two individuals are first cousins) and zygosity (twins) test (determines whether two individuals are monozygotic or dizygotic twins).
As with a parentage test, a specific index is calculated to indicate the likelihood of there being a biological relationship.

[back to top]

Substance Misuse
Conventional “drugs”, which can be defined as any substance that is used to modify a chemical process or processes in the body, for example to treat an illness, relieve a symptom, enhance a performance or ability, or to alter states of mind. A number of laws have been implemented in the UK to control the manufacture and supply of medicinal drugs (Medicines Act 1968) and prevent the misuse of non-medicinal drugs (Misuse of Drugs act 1971). Non-medicinal drugs are the drugs used for recreation and comprise mainly of psychoactive drugs, drugs that that affects the brain to produce alterations in mood, thinking, perception and behaviour. There are four main ways by which they exert their effects; depress the nervous system, stimulate the nervous system, reduce pain & alter perceptual function
In order to have the desired effect the drug must first be absorbed into the body, this can occur via various routes which include; Ingestion, Inhalation, Intravenous Injection & Intranasal Administration. The drug is converted by enzymes in the body into specific pharmacological metabolites which are excreted, most commonly via urine, but also by salivary glands, sweat glands or incorporated into growing cells/tissues (hair cells- figure 2). Detection of drug misuse is evidenced by the presence of metabolites within the sample of blood, urine, saliva or hair. The choice of sample is determined by the specific objective, as each sample type has its own advantages and disadvantages, for example, the window of detection for a drug to be detected in urine/blood is 3-6 days (depending upon the drug). Therefore to establish that the drug was consumed recently a urine/blood analysis would be the best choice. However, if chronic misuse of a substance needs to be established, then hair analysis would be the better sample to use. Of course other factors such as possibility of adulteration of the sample, storage of sample, ease of collection and expense should all be taken into consideration.














The first stage analysis, known as a screening is performed by Enzyme Linked Immuno Sorbant Assay (ELISA) that detects not only traces of drugs but their metabolites; these are chemicals that appear only when the body has converted the drug.
If a positive result appears than a second stage process known as a confirmation test is performed and the sample results are confirmed by gas chromatography/mass spectrometry (GC/MS). This second test has a cutoff level to eliminate specimens containing drug levels that could arise from environmental exposure. To be considered positive a sample must show the presence of the drug in these two different assays. This two step analysis protects against false positive reports.

The Parliamentary Office of Science and Technology states in a report published on Drug Testing in the UK: ‘Gas chromatography-mass spectrometry (GC-MS) is considered by the Forensic Science Service the gold standard in hair testing. It is usually the only test which is accepted in the Courts. GC-MS is the tool of choice because it has good sensitivity, selectivity, specificity, a high degree of standardization, sample throughput, and instrument ruggedness’ (POST note 28, 2004)

[back to top]

Alcohol Abuse
Alcohol Abuse has increasingly become a major public health problem with far reaching consequences not only for the individuals concerned but for their families and for society as a whole. It is estimated that 10% of the population have medical problems. Alongside the general toxic effects alcohol has on cells in the body, heavy or prolonged use of alcohol can lead to more serious psychological damage such as: depression, aggression, dependency and impairment of judgment, all of which have detrimental effects for an individual’s capacity to take care of dependants. Over the years there have been a number of biochemical tests developed that contribute to the diagnosis and treatment of alcohol consumption.

[back to top]

Ethyl Glucuronide detection via Hair Analysis
Ethyl glucuronide (EtG) is a product of alcohol metabolism and is considered a promising marker for alcohol consumption. However, the value of its measurement in blood or urine is low due to its relatively rapid elimination from these matrices.
As with drugs, metabolites of alcohol consumption can be bound into keratinised material (nails and hair) and these provide a window of detection that can run into several months.
The detection of ethyl glucuronide confirms alcohol consumption and thus it is useful in monitoring recovering alcoholics to ensure abstention. A negative result does not confirm abstention due to variations in the binding ability of the hair. However, if it is shown to be present in hair that is known to have grown during the subjects active use of alcohol, then its absence in fresh hair growth provides strong support for the view that the person is abstaining from its use. Its continued detection some months after the last supposed intake would confirm that the patient has relapsed.
Ethyl glucuronide is very rarely detected in a social drinker and thus it provides a marker of alcohol abuse and as such can be useful in pre-employment and workplace testing. Abusers of alcohol are known to have a high absence rate and there is the obvious risk of impairment in their motor functions that can put themselves and others at risk if they are engaged in the operation of machinery. Thus hair and nail testing for EtG provides a valuable tool both in economic and Health and Safety terms.

[back to top]

Determination of metals and trace elements in blood, urine and hair specimens
Blood, urine or hair samples can be used to evaluate a passive or a professional exposure to heavy metals.
Arsenic Seafood, wood preservatives (fungicides), weed killers, anticorrosive agents, alloys with lead and copper...
Lead Paintings, batteries, food containers (can, piping)...
Mercury Batteries, amalgam, vacuum pumps, valves, joins...
Cadmium Batteries, tires, plastics, cigarette smoke...
Aluminium Welding, food...

[back to top]

Copyright © eurofins forensic services – 2007 | All rights reserved