Genetic print

Analysis of genetic print , also called " signature génétique" or " test DNA " , is a technique which makes it possible to identify an individual starting from a simple small sample of DNA, but also to seek a filiation (test of paternity). This method was developed by Sir Alec Jeffreys of the University of Leicester in 1985.

This method rests on the following fact: although two human has a vast majority of their identical DNA, a certain whole of sequences in the DNA remain specific to each individual. These are these sequences that the analysis of genetic print proposes to study. Indeed if a sample of cells presents the same genetic print that an individual, one can affirm that these cells come from this individual. In its initial meaning, the expression genetic print , of English Genetic fingerprint , is formed by analogy with the digital fingerprints, used within the framework of the identification of the criminals, and who are specific to each individual.

In a meaning broader and lending to confusion, a genetic print indicates for some the result of any analysis DNA, which takes the shape of bands of electrophoresis on freezing of agarose.

locus. By using PCR to detect the number off repeats At several loci, it is possible to establish has match that is extremely unlikely to cuts arisen by coincidence, except in the box off identical twins, who will cuts identical genetic profile. -->

The genetic prints are used in Legal medicine to identify or clear suspects thanks to their Sang, them Salive, their Poils or them Sperme. They also make it possible to identify human remainders, to make Test of paternity, to organize the Donation of organs, to study populations of wild animals or to even generate assumptions on the human Diaspora at the time of the Préhistoire.

Of course, because of the significant character of this information, the tests are subjected to legal constraints, for example, in France, the national Advisory committee of ethics indicated: “Out of civil and family matter, the unavailability of the civil identity and the filiation, whose establishment does not require a biological proof apart from a lawsuit, the safety of the parental bond in the paramount interest of the child, the balance and the peace of the families, justify that the biological proof can be reported only under the control of the judge, within the framework of an legal action relating to filiation and juridically admissible”.

Extensive The United Kingdom currently has the most DNA database in the world, with well over 2 million records ace off 2005: National The DNA Database (NDNAD). The size off this database, and its spleen off growth, is giving concern to Civil liberties groups in the U.K., where police force cuts wide-ranging powers to take samples and retain them even in the vent off acquittal.

DNA fingerprinting methods DNA fingerprinting begins by extracting DNA from the concealments in has sample off blood, salivated, semen, but other appropriate fluid gold tissue. Refer samples are often collected using has oral Swab. -->

General principles

The DNA consists of sequences of 4 nucleotides has, C, T, G.

It should be recalled that the Gène S allow the manufacture of the Protéine S. But there exists on the DNA of the portions which do not code any protein. It some of them is called Microsatellites and Minisatellite, which is specific to each individual and constitutes his genetic signature.

They are repeated sequences of DNA. It there a:

the short Sequences repeated S out of tandem, also called Microsatellite S or (STR) for Shorts Tandem Repeats in English. The majority of the repeated sequences are repeated of 4 Nucléotide S, but the lengths from 2 to 5 bases are also studied. Example:

the Minisatellite S or VNTR for Variable Number Tandem Repeats . The repeated sequences are repeated from 10 to 100 nucleotides. One gathers sometimes these methods under the name Multiple Loci VNTR Analysis (Mlva).

These areas of the DNA are very polymorphic S: indeed, the number of repetitions is variable for each individual. Because people do not have the same number of repeated, these areas of the DNA make it possible to identify the individuals.

The area of the chromosomes where these sequences (their Locus) are must be located, then amplified by PCR: it is a question of manufacturing the many ones copies this DNA so that this one is “visible” at the end of the analysis. The fragments of DNA obtained are separated and identified by electrophoresis. This makes it possible to know their length and thus to deduct the number of repetitions from it.

The 2 methods of the most common separations are the capillary electrophoresis and electrophoresis on freezing.

Reliability

The great force of the system baseds on the microsatellites is the statistical reliability of the identification.

The polymorphism of each microsatellite is by itself very variable. A version of same a Locus (or Allele) can have a frequency ranging between 5 and 20% of the individuals. Only one locus thus does not make it possible to designate a precise individual. Several loci should be used.

In France and in the United States, one usually uses 13 Loci (areas of repeated sequence) for an identification. And as each locus of a certain sequence of repetition (microsatellite is composed) and than the number of repetition is perfectly independent of the repetitions on the others loci, the rules of statistics can be applied.

For example, for three loci has, B and C, independent, and for which there exist several versions (A₁, A₂, A₃, and B₁, B₂,…) , one can say that Probabilité (A₁, B₂, C₁) =Probability (A₁) X Probabilité (B₂,) X Probabilité (c₁). Thus for 13 loci, the probability of having two identical sequences for 2 different individuals is estimated at 1 chance on 10¹⁸, which is almost negligible (very near to zero). Consequently, more the number of microsatellites analyzed is important, more the identification is reliable.

According to the countries various, various systems of identification DNA bases on the repetition of the microsatellites are used. In North America (the USA, Canada), standard Codis is used, whereas in England, it is SGM+.En France, the genetic prints are gathered in the national Fichier automated of the genetic prints (FNAEG).

But in any case, several zones of microsatellite of which common to the various standards used, which allows compatibility between them.

STR analysis The most prevail method off DNA fingerprinting used today is based one PCR and use Short tandem repeat S (STR). This method use highly polymorphic areas that cuts shorts repeated sequences DNA off (the most common is 4 bases repeated, goal there are lengths in uses, including 3 and 5 bases). Different Because people cuts different numbers off repeat units, thesis areas off DNA edge Be used to discriminate between individuals. Thesis STR loci (hirings) are targeted with sequence-specific primers and are amplified using PCR. The DNA fragments that result are then separated and detected using electrophoresis. There are two common methods off separation and detection, Capillary electrophoresis (EC) and Freezing electrophoresis.

The polymorphisms displayed At each STR area are by themselves very common, typically each polymorphism will Be shared by around 5 - 20% off individuals. Multiple When looking At loci, it is the single combinations off thesis polymorphisms to year individual that makes this method discriminating ace year identification tool. The more STR areas that are tested in year individual the more discriminating the test becomes.

From country to country different STR based DNA profiling systems are in uses. In North America Codis is prevail, while in the U.K. the SGM+ system, which is compatible with The National DNA Database is in uses. Whichever system is used, many off the STR areas under test are the same. Thesis DNA profiling systems are based around multiplexing reactions, whereby many STR areas will Be under test At the same time.==Les methods of analysis ADN.==

The analysis of the DNA begins with the extraction of the molecule of DNA of the cells contained in the samples. These samples can be blood, saliva, sperm or all other fluids or body fabrics adequate. -->

Various techniques of analysis

It is initially necessary to practice the Extraction of the DNA of the sample of cells. It is then necessary to target and analyze the repeated sequences. The method by PCR is used.

The method PCR

Method RFLP

AmpFLP

Another technique, AmFLP or Amplified fragment-length polymorphism were used with the beginning of the year 1990. This technique is faster than the analysis RFLP and uses the technique of the chain reaction by polymerase to retort the samples of DNA.

One distinguishes different the Allèles by polymorphism from the Répétition out of Polymorphic Tandem (variable number tandem repeat - English VNTR-) separated by electrophoresis on freezing polyacrylamide using a scale from measurement from alleles (in opposition to the scales of molecular weight).

The bands of migrations can be visualized by coloring freezing with the money. One of fragments DNA the most used for the AmpFLP analysis is locus D1S80. Like all methods based on the chain reaction by polymerase, the DNA severely degraded or in very minor amounts, can produced marginal alleles retorted in insufficient quantity which can cause errors. For example, one could conclude with twists with a DNA Homozygote whereas it would be Hétérozygote. Moreover, as the analysis is carried out on freezing, the Répétitions out of Polymorphic Tandem of great numbers can accumulate in top of freezing making interpretation difficult.

AmFLP is an easily automatizable method which allows the phylogenetic creation of Classification on the comparison of individual DNA

Because of its relatively modest cost and its facility of installation and exploitation, the AmFLP analysis remains widespread in the laboratories having little means or little requirement.

Technical Another, AmpFLP, gold Amplified fragment length polymorphism was also could into practice during the early 1990 ' technical S. This was also faster than RFLP analysis and used PCR to amplify DNA samples. Variable It relied one number tandem repeat (VNTR) polymorphisms to distinguish various alleles, which were separated one has Polyacrylamide freezing using year allelic ladder (ace opposed to has molecular weight ladder). Bands could Be visualized by Silver staining the freezing. One popular locus for fingerprinting was the D1S80 locus. Ace with all PCR based methods, highly degraded DNA gold very small amounts off DNA may causes allelic dropout (causing has mistake in thinking has heterozygote has homozygote) gold other stochastic effects. In addition, because the analysis is gives one has freezing, very high number repeats may bunch together At the signal off the freezing, making it difficult to solves. AmpFLP analysis edge Be highly automated, and allows for easy creation off Phylogenetic trees based one comparing individual samples off DNA. Had to its relatively low cost and ease off set-up and operation, AmpFLP remains popular in lower income countries. -->

Analyzes by random Amplification of polymorphic DNA

Capillary electrophoresis works by electrokinetically (movement through the application off year electric field) injecting the DNA fragments into has thin knell tubes (the capillary) filled with polymer. The DNA is pulled through the tube by the application off year electric field, separating the fragments such that the smaller fragments travel faster through the capillary. The fragments fluorescent are then detected using dyes that were attached to the primers used in PCR. Multiple This allows fragments to Be amplified and run simultaneously, something known ace multiplexing. Sizes are assigned using labeled DNA size standard that are added to each sample, and the number off repeats are determined by comparing the size to year allelic ladder, has off sample that contains all the common possible repeat sizes. Expensive Although this method is, larger capacity machines with higher throughput are being used to lower the cost/sample and reduce backlogs that exist in many government crime facilities.

Freezing electrophoresis acts using similar principles ace EC, goal instead off using has capillary, has broad polyacrylamide freezing is used to separate the DNA fragments. Year electric field is applied, ace in EC, goal instead off running all off the samples by off has detector, the smallest fragments are run closed to the bottom the freezing and the entire freezing is scanned into has computer. This produces different year image showing all off the bands corresponding to repeat sizes and the allelic ladder. This approach does not require the uses size off standard, since the allelic ladder is run alongside the samples and serfs this purpose. Visualization edge either Be through the uses off fluorescently tagged dyes in the primers gold by silver staining the freezing prior to scanning. Effective Although it is cost and edge Be rather high throughput, silver staining kits for STRS are being discontinued. In addition, many labs are phasing out gel in favor off IT ace the cost off machines becomes more manageable. -->

DNA mitochondrial analyzes

The analysis of DNA mitochondrial (ADNmt) does not make it possible to identify at 100% an individual, but makes it possible to exclude an assumption, because this DNA does not present enough variability in the populations. In light, as several people can present same ADNmt, one will not be able to determine to which these people a sample of ADNmt belongs. There is approximately 1 chance out of 2000 that two nonrelated people present same the ADNmt.

The medical examiners study sites HV1 and HV2 of ADNmt. These are sequences hypervariables (HV) whose various versions are numerous and with relatively weak frequencies (a few % of the general population). Consequently these markers cannot determine if a sample comes from a single person. One will be able to always propose a probability that the sample comes from a precise individual, but that does not constitute an unquestionable proof. On the other hand, if one obtains 2 ADNmt different one can be sure that it is not a question of the same person.

; Favors For strongly degraded samples or on a hair without bulb, it is sometimes impossible to obtain a complete profile of all the Microsatellite S. In this case, one can use DNA mitochondrial (DNA MT) because there are of them many copies in a cell, while there is seldom more than 1 or 2 copies of nuclear DNA.

; Technique The medical examiners amplify sites HV1 and HV2 of ADNmt; they séquencent then each area and compare each Nucléotide. It is generally considered that the DNA MT tested is not similar to that of reference when a difference of more than two nucleotides is noted.

As the DNA MT is transmitted only by the mother, this reference is the DNA MT of one of the people of the maternal line.

The analyst must show a little understanding because the Hétéroroplasmie and of the differences poly-C can scramble comparisons of sequences.

DNA MT is useful in the determination of not very clear identities, as those of missings if a relative maternellement dependant can be found.

The analysis of the DNA MT was used to prove the imposture of Anna Anderson which was claimed to be the Russian princess Anastasia Romanova. Heteroplasmy and poly-C differences may throw off straight sequence let us comparisons, so nap appraises one off the share the analyst is required. mtDNA is useful in determining unclear identities, such ace those off missing let us persons when has maternally linked relative edge Be found. mtDNA testing was used in determining that Anna Anderson was not the Russian princess she had claimed to Be, Anastasia Romanov.

mtDNA edge Be obtained from such material ace to hate shafts and old bones/teeth. -->

Analysis of the Y chromosome

There exists on the Y chromosome areas hypervariables, named STRY. ; Disadvantage The Y chromosome is present only at the individuals of male sex. It will not poura being carried out on a woman. ; Advantages The Y chromosome is transmitted by the father, and analyzes it of this chromosome allows to make the tests of paternity, when the father is not alive any more. For example, one could clear up the controversy on Sally Hemings while determining that Thomas Jefferson would have had a son with this slave well.

Legislative and legal aspects

Discussion goshawks of the evidence by test DNA

When using RFLP, the theoretical risk off has coincidental match is 1 in 100 billion (100,000,000,000). However, the spleen off laboratory error is almost certainly higher than this, and often actual laboratory procedures C not reflect the theory under which the coincidence probabilities were computed. -->

At the beginning of tests DNA like legal evidence, the lawyers argued that given that the probability of having the same genetic card, was of 1 out of 5 million, a population of 60 million, there were statistically 12 people having the same results with tests DNA. They thus considered that the probability was not 1 per 5 million but 1 out of 12. This argument cannot be retained unless the suspect was drawn randomly in the population. However generally, the suspect was apprehended for other reasons that the genetic print.

When analyzes RFLP were developed, the theoretical risk fell to 1 out of 100 billion. Nevertheless, the rate of handling error is surely higher than the theoretical risk because often the current procedures do not reflect the way in which the probability of coincidence is calculated.

precisely the same hiring, goal has laboratory worker may conclude that similar -- goal not precisely identical -- band patterns result from identical genetic samples with sum imperfection in the agarose freezing. However, in this box, the laboratory worker increases the coincidence risk by expanding the criteria for declaring has match. Recent studies cuts quoted relatively high error spleens which may Be causes for concern. Because off this, arbitrary ceilings were could one match probabilities used in RFLP analysis than the theoretically computed ones. Today, RFLP has become widely disused due to thesis difficulties in interpretation. -->

For example the probability of coincidence is based on the probability that 2 markers in 2 samples cause a band “exactly “at the same place. But a laboratory assistant could conclude that a network of band similar, but not completely identical, is in fact the same sample parce these differences are due to imperfections of handling like a difference in freezing of agarose. In this case, the laboratory assistant, increases the risk of error while derogating from the criteria of recognition. Recent studies evaluated the risk on a sufficiently high level to cause dispute

Because of that, arbitrary ceilings of probability, higher than those calculated, were put on analyzes RFLP. Today, analyzes RFLP are largely unutilised because of these difficulties of interpretations.

Analyzes STR do not suffer from the subjectivity of the laboratory assistants, and allows much better a precision of distinction of individual (about 1 out of 10 with a complete print).

In any case, analysis DNA must be taken account within the framework of a context especially so of other elements make it less reliable. Thus, the contaminations of sample by other evidence (secondary transfer) is a source of error often evoked by defense counsels.

More rarely, the cases of dream genetic are one possibilities where nonthe genetic agreement clears with twists a suspect

Could it Be year accidental random match?

Yew not, could the DNA sample cuts been planted?

Yew not, did the accused leave the DNA sample exact At the time off the crime?

Yew yes, does that mean that the accused is guilty off the crime? -->

If test DNA is positive, one must put the following questions:

Can there is to have a random coincidence?
So not, was the sample polluted?
So not, did the suspect leave this DNA to the moment of the crime?
If so, that means that the defendant is guilty crime.

Fake DNA obviousness The been worth off DNA obviousness has to Be seen in light off recent boxes where criminals planted fake DNA samples At crime scenes. In one box, criminal even planted fake DNA obviousness in his own body has: Patient Dr. John Schneeberger off Canada raped one off his sedated in 1992 and left semen one her underwear. Drew Schneeberger' S blood and compared its DNA against the crime scene semen DNA one organizes three occasions, never showing has match. It turned out that He had surgically inserted has Penrose drain into his ARM and filled it with foreign blood and Anticoagulant S. -->

Errors due to analyzes DNA

One can see the relevance of analyzes DNA as legal evidence in the light of recent businesses where the criminals left samples of “false” DNA on the scenes of crimes. In a business, a culprit even dissimulated the false DNA in his own body: in 1992, Doctor John Schneeberger in Canada violated one of his patients by doping it before. The Police force made a blood test with Schneeberger and compared it with the DNA found on the scene of the crime. To 3 recoveries without never noting an agreement the 2 DNA enters (that of sperm and that of blood).

It proves that the doctor had been surgically established in the arm a Penrose drain filled of a mixture of anticoagulants and blood of someone else.

Remarkable cases

Anna Anderson claimed that she was Princess Anastasia Romanov off Russia; in the 1980s her cremated remains were tested and seemed to show --that she was No relation to the Romanov. --> In the years 1920, Anna Anderson declared that it was the large-duchess Anatasia Romanova of Russia. In the years 1980, its ashes of cremation were tested and show that it did not have any family ties with the remaining members of the line of the Romanov.

The technique of the genetic prints developed by Alec Jeffreys was used for the first time in 1986 in a business judged by a Court of Pennsylvania.

Leicester, the city where it was first discovered. --> In 1987, the baker English Colin Pitchfork was the first criminal confused by an analysis DNA, with Leicester, the city where were developed the techniques of analysis DNA.

Florida rapist Tommie Lee Andrews was the first person in the United States to Be convicted ace has off result DNA obviousness, for raping has woman during has burglary; He was convicted one 6 November 1987 and sentenced to 22 years in prison. --> The November 6th 1987, in Florida, the rapist Tommie Lee Andrews was the first nobody with the the United States with being condemned to 22 years of prison by an analysis DNA, for the rape of a woman during a burgling.

Chicago man Gary Dotson was the first person whose conviction was overturned using DNA obviousness. --> In 1989, with Chicago, Gary Dotson was the first suspect cleared by a test DNA.

1992, DNA obviousness was used to prove that Nazi doctor Josef Mengele was buried in Brazil under the name Wolfgang Gerhard. --> In 1992, a test DNA proved that the Nazi sadly celebrates doctor Josef Mengele was buried with the Brésil under the name of Wolfgang Gerhard

O.J. Simpson to has double murder. The puts also brought to light the laboratory difficulties and handling procedure mishaps which edge causes such obviousness to Be significantly doubted. --> In 1994, O.J. Simpson was discharged whereas the charge was persuaded to have presented a solid dossier and awaited a judgment. In particular, expertises DNA were criticized hard by the defense which denounced the disordered procedures having contaminated the samples.

In 1994, tests DNA on hairs of cat made it possible to condemn a man for the murder of his wife. It was a first in the history of legal medicine, of the use of a nonhuman DNA to identify a criminal.

In 1998, Doctor Richards J Schmidt was convinced of attempted murder to the second degree when it was shown a bond between the DNA of the viral strain HIV which it was shown to have inoculated with his partner and that of one of its patients reaches Sida. It was it first time that a viral DNA was used as incriminating evidence.

In March 2003, Josiah Sutton was slackened after having purged 4 years of prison on 12 for its judgment for sexual assault. The samples of doubtful DNA were retestés, like many others, after the discovery of serious negligences at the laboratory of the Police force of Houston The trial off notable Robert Pickton is in that DNA obviousness is being used primarily to identify the victims , and in many boxes to prove to their existence. -->

In June 2005, with an analysis DNA, Halstead Refusals, John Kogut and John Restivo gained their revision of lawsuit following their sentence for murder. The three men had already carried out eighteen years over the thirty years of custodial sentence.

The lawsuit Robert Pickton is remarkable because in this case analyzes DNA were used mainly to identify " victimes" and in many cases to prove their existence.

Exculpation of shown and of condemned

Earl Washington is released on February 12th, 2001 after nine last years in the corridor of the dead one: he had acknowledged in 1982 the rape and the murder of an young woman and had been condemned to the capital punishment although no material proof could be retained against him.

In December 2005, Robert Clark was cleared for an aggression on a woman in 1981 in Atlanta after 24 years of detention, because he had eaten a green apple. Mr. Clark is the 164e nobody with the the United States, 5th in the State of Georgia to being released after judgment by a test DNA.

Test DNA and Frenchwoman bill on immigration

In 2007, in France, where a law of Bioéthique frames tests DNA, a polemic is raised when the government and the National Assembly propose, on the basis it voluntariate, to make tests DNA on foreigners wishing to immigrate legally within the framework of the Family gathering and to rather prove by a biological test than by an administrative proof sometimes non-existent, filiation between the applicant to make come his family and those presented like its Enfant S.

Members of Parliament and intellectuals opposed this amendment suggested by the deputy Thierry Mariani.

A petition launched by the satiric weekly Charlie-Hebdo and association S.O.S Racism gathered tens of thousands of signatures. Within the government, the Foreign Minister Bernard Kouchner and Fadela Amara, the Secretary of State in charge of the policy of the City, opposed this law; Fadela Amara declared, “there has enough that one instrumentalise each time immigration, for very precise reasons. I find that disgusting! ”. The philosopher and essay writer Pascal Bruckner supported it in a plea condemning this amendment.

Tests DNA are used in eleven European countries, of which Germany, Italy, and the United Kingdom.

Since November 2007 several companies in Iceland and in the USA put on line genetic databases: with the help of a sum of approximately thousand dollars, each one can make draw up its genetic profile (by the method of the SNP Single Nucletoid Polymorphism) and compare with the data of the base to consider its risk to develop a genetic disease, to reconstitute its probable family origins, etc Of other companies still offer less expensive genetic tests (100 dollars approximately) which make it possible to choose the method of slimming or the cream anti-ageing best adapted to its genotype, claims which do not have, obviously, no scientific base.

External bonds

clear and complete File on the site Planètegène .
Example of expert report following analyzes DNA in the businesses of the “missings of Mourmelon”. ===en anglais===
How DNA Obviousness Works
DNA Typing: Technical, BASIC & Ethical Matters
How to make have DNA (genetic) off Fingerprint and applications DNA Fingerprinting
Create has DNA Fingerprint
eQMS:: DNA DNA Fingerprint Software

References

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