It is worth considering the contamination at the beginning of this discussion because this is a well known limitation. Unfortunately, contamination of importance in pcr is often underestimated. Dna pcr copies efficiently if the initial dna is in good condition. Dna single entity be millions or billions of dna molecules in about three hours. The pcr process is sometimes compared to a xerox machine and made many copies. Although initially, it is a useful comparison, does not communicate the true nature, the chain reaction pcr. In pcr, the original dna is copied, then copies are copied, copied the copies and so on. This results in a dramatic increase in the amount of dna that could not easily be carried out on the analogy of photocopies. The pcr process deserves classification as a "chain reaction", as it has much in common with other chain reactions, such as avalanches.
The pcr is also very similar to what happens when a clinical infection. Doctors have known for many years that a single germ cells (bacteria or virus), contamination of a wound can cause a massive infection. Similarly, a dna molecule can contaminate (infect) a pcr and become a major problem. The ability of small amounts of dna to produce false and misleading is well known and well documented within the research community, where the technology originated. Anyone who has caught a cold of unknown origin or who have an allergy to pollen must have some sense of ease with pcr are contaminated. In fact, it is probably easier to contaminate a pcr to catch a cold because unlike our bodies, itp immune system failure. The only protection that itp is the technique of the analyst, the use of control samples to monitor pollutants and careful interpretation.
Prevention of false results involves the use of carefully applied controls and techniques. As described below, controls and techniques rarely can ensure that contamination has not influenced the results. In forensic dna testing, some of the worst scenarios scientifically cases can be prevented by keeping the dna samples of individuals well known outside the reach of other items of evidence in all stages. Most forensic dna laboratories to perform negative controls, blank samples are often detected contaminants in the laboratory. Blanks contaminant detection, dna profiles showing partial or total representing contaminants. Moreover, the blank may not show the profile, in line with, but does not prove that the contamination did not occur. Unfortunately, some forensic dna laboratories ignore its controls. In favor of some of the controls by using special equipment in them, or by failing to conduct throughout the proceedings. These practices are dangerous, especially when an important test sample has a low amount of dna, degraded dna, or not presented as a minimum sample or partial (see below). In summary, while the pcr is a useful research tool, all applications require very careful monitoring.
The pcr is also very similar to what happens when a clinical infection. Doctors have known for many years that a single germ cells (bacteria or virus), contamination of a wound can cause a massive infection. Similarly, a dna molecule can contaminate (infect) a pcr and become a major problem. The ability of small amounts of dna to produce false and misleading is well known and well documented within the research community, where the technology originated. Anyone who has caught a cold of unknown origin or who have an allergy to pollen must have some sense of ease with pcr are contaminated. In fact, it is probably easier to contaminate a pcr to catch a cold because unlike our bodies, itp immune system failure. The only protection that itp is the technique of the analyst, the use of control samples to monitor pollutants and careful interpretation.
Prevention of false results involves the use of carefully applied controls and techniques. As described below, controls and techniques rarely can ensure that contamination has not influenced the results. In forensic dna testing, some of the worst scenarios scientifically cases can be prevented by keeping the dna samples of individuals well known outside the reach of other items of evidence in all stages. Most forensic dna laboratories to perform negative controls, blank samples are often detected contaminants in the laboratory. Blanks contaminant detection, dna profiles showing partial or total representing contaminants. Moreover, the blank may not show the profile, in line with, but does not prove that the contamination did not occur. Unfortunately, some forensic dna laboratories ignore its controls. In favor of some of the controls by using special equipment in them, or by failing to conduct throughout the proceedings. These practices are dangerous, especially when an important test sample has a low amount of dna, degraded dna, or not presented as a minimum sample or partial (see below). In summary, while the pcr is a useful research tool, all applications require very careful monitoring.
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