DNA forensics

The sequence of all species of organisms can be identified by studying the DNA that is unique to this species. Identify individuals within the species is less accurate on the site, but if DNA sequencing technology, further development of direct comparison with the large DNA and possibly the entire genome of a viable and practical and allows you to clearly separate identity.

Identifying persons forensic scan 13 loci, or regions, which vary from person to person and use these data to create a DNA profile of the person (also called DNA fingerprinting). There is very little chance that another person with the same DNA profile of a specific set of 13 regions.

Some examples of the use of DNA for forensic identification

* Identification of the suspects, who can match DNA evidence left at the crime scene sites
* People to exclude falsely accused of crimes
* Recognition of victims of crime and natural disasters
* Establishment of paternity and other family relationships
* When determining the risk and protected species as an aid to wildlife officials can (be used for prosecuting poachers)
Detection of bacteria and other microorganisms that may contaminate air, water, soil and food
* Party organ donors with recipients in transplant programs
* Place rocks seeds or livestock
* The authenticity of food as caviar and wine

DNA is effective in identifying people?

DNA identification can be very effective if it is used to make sense. Parts should be changing the DNA sequence between the most use, in addition, the parties must be large NOK overcome the fact that the man is completely random mating.

Included in the State to investigate the crime. . .

We assume that blood is the conclusion to the scene. Type O occurs in approximately 45% of Americans. If investigators type only for ABO, finding that the suspect in a crime type O really does not talk too much.

If, in addition to the type of Ø, the suspect blond, blond and questions, you now have two pieces of evidence suggest that it was in reality. Nevertheless, there are a number of type O is a blonde.

If you are at the crime scene traces from a pair of Nike Air Jordan (unique design of the herd) and the suspect, because type O and blond, Air Jordan also works the same design of the crowd much closer to the samples of the suspect to the scene.

Thus, to collect evidence of a link in the chain, where each bit is not even a strong, but the version of each of them, very strong, we can say that they doubt that the human rights.

Since DNA is the same type of thinking, which is used, you can search for matches (on the basis of the order, or if the number of small repeating units of DNA sequences) in different locations in the human genome, one or two (even three) NOK not be sure that the right course, and thirteen sites use. Rare appearances in all twelve good that you (or perhaps the prosecutor or the jury) the strengthening of trust ( "beyond reasonable doubt") argue that human rights.

How DNA typing done?

But the tenth of a percent of DNA (about 3 million bases) differs from one person to another. Researchers can use the variable regions to create a DNA profile of the person, using samples of blood, bones, hair and other body tissues and products.

In criminal cases in question, as a rule, get samples of evidence from the crime and suspicious cases, DNA extraction and analysis of the current set of specific regions of DNA (markers).

Scientists find evidence of DNA samples through the development of small pieces of DNA (probes) that each query, and bind to complementary sequences of DNA in the sample. Creates a number of investigations related to the specific structure of the samples of human DNA. The scientists compare the DNA profiles of the law to determine appropriate evidence test sample. Mark himself, as a rule, not only for the individual, but in two samples of DNA that are similar to four or five regions, most likely that the samples of the same person.

If the sample does not match the profile, not the person placing the DNA at the crime scene.

If the nature of the suspect can be assisted in the sample. Although the likelihood that another person with the same DNA profile of a specific set of probe, the chances are very small. Q: How small probability must be convinced of the guilt or acquittal of the innocent right? Judges consider many of the materials in the jury considered in conjunction with other evidence in the case. Experts say that the technology of recombinant DNA-based forensic best of witnesses, where the probability of a correct definition in 50:50.

More probes used in DNA analysis, most likely from a template, and the occasional match, but each one must probe further increases the time and cost of testing.Recommended four to six sensors. Try to get some more conventional probes, observed John Hicks (Alabama State Department legal services). He predicted that the DNA chip technology (in thousands of short sequences of DNA data to insert a small chip) will be done much faster economic analysis using probes much larger and increases the probability of intersection of the parties.

What are some of the field of DNA technologies used in forensic investigations?

Excerpts restrictions Polymorphism (RFLP)
RFLP technique to analyze a variable length of DNA fragments resulting from digestion of DNA samples from a special type of enzymes. This enzyme, restriction endonuclease meetings on specific model of DNA sequences, known as restriction endonuclease recognition site. Creates the presence or absence of specific recognition sites in DNA of different length DNA fragments separated by electrophoresis education. Thus hybridization with DNA probes linked to the complementary sequences of DNA in the sample.

RFLP was one of the first applications of DNA analysis in forensic investigations. With the development of new and more efficient DNA-analysis techniques, RFLP is not used as much as it was before, because it requires relatively large amounts of DNA. In addition, samples of degraded environmental factors, such as dirt, and mildew, do not work well with RFLP.

PCR
Was used for chain reaction (PCR) to make millions of exact copies of DNA from biological samples. DNA amplification by polymerase chain reaction can analyze DNA from biological samples as small as a few skin cells. For RFLP, if the amount of quarter samples of DNA. The ability of PCR for amplification of small amounts of degraded DNA samples is the analysis. Care, however, should be adopted in order to prevent contamination with other biological material to identify, collect and preserve samples.

Street Analysis
SSR (str) technology is used to evaluate specific regions (loci) in the nuclear DNA. The diversity of regions, size can be used to distinguish one DNA profile from another. Federal Bureau of Investigation (FBI) uses a standard set of specific regions from 13 to St. CODIS. CODIS is a program that controls the local state and national DNA databases of convicted persons, unsolved crime scene and evidence of missing persons. The probability that two individuals of the same 13 loci of a profile in one billion.

Analysis of mitochondrial DNA
Analysis of mitochondrial DNA (mtDNA) can be used to study DNA samples can be analyzed by RFLP or size. Nuclear DNA must be extracted from the samples for use in RFLP, PCR, and size, however, mtDNA analysis uses DNA extracted from other cellular organelles mitochondria. Although adult biological samples may be missing the main cell materials, such as hair, bones and teeth, which analyzed the numbers and RFLP, could be analyzed with mtDNA. During the investigation, the case went unsolved for many years, mtDNA is extremely valuable.

All mothers are the same mitochondrial DNA to their children. This is because the mitochondria of each new embryo from the egg mother. Father's sperm contributes only nuclear DNA. Compared with the profile of mtDNA remain unknown to the profile of a potential maternal relative can be an important technique with the lack of research on human beings.

Y-chromosome analysis
Y-chromosome is passed directly from father to son, so that the analysis of genetic markers on the Y chromosome is especially useful for tracking relationships between men and for analysis of biological evidence involving multiple male contributors.