This sequence is also known as a Short Tandem Repeat, or an STR for short. A unique STR exists when two or more base pairs appear in a certain and repetitive pattern, and also when this exact pattern is repeated close by in adjacent spots. It should be noted that the STR is typically anywhere from two to four nucleotide base letters, and even larger patterns, known as Variable Number Tandem Repeats, or VNTR for short, can contain up to eighty letters. This thus provides for a much higher degree of accuracy and probability. But, the analysis can take up to days to complete, not just a matter of a few short hours.
There are two kinds of DNA which are currently present in all living beings, and they are as follows:
- Nuclear DNA: This is the contribution of genetic components from both the mother and the father, and is most commonly found in the blood, saliva, semen, and even the bones;
- Mitochondrial DNA: This is the contribution of genetic components from the mother only, and can also be found in the hair and the teeth. This is the type of DNA which is used to identify missing individuals.
The Characteristics of DNA Recognition
The raw DNA sample can be collected from blood, semen stains, saliva, hair, or even under voluntary conditions. With the latter approach, a buccal swab can be very easily inserted into the mouth, in order to collect a sample of DNA. After the DNA sample is collected from the specific source, the DNA is then isolated, and then further divided into much shorter segments (also known as restriction enzymes) which terminate the DNA strands at various points, and differentiated in size using an electric current.
The differentiated sizes are then placed onto a nitrocellulose filter which possesses different fluorescent dyes, which then further attach themselves to the differing repeating patterns. This is then X-rayed, and the resultant image is a DNA fingerprint. An image of a DNA strand can be seen in Figure 9.
Subsequently, this DNA fingerprint is then translated into a DNA profile which displays the number of STR’s at the specific locations. The DNA markers used to construct this DNA profile are located on chromosome numbers 1, 2, 4, 5, 10, and 17. These specific locations are referred to as DNA loci. After this profile is constructed, the findings occur in one of the following three categories:
- Exclusion: This result possesses the highest level of certainty (meaning, the raw data is different from the source it was collected from);
- Non Exclusion: The raw data cannot be excluded of coming from the same source (in other words, the raw DNA sample and the source from which it was collected from are the same);
- No Result: No conclusions can be drawn.
Because DNA recognition is still under heavy research and development, it can only be matched up against five of the seven criterion, which are as follows:
- Uniqueness: Amongst all of the other biometrics, DNA possesses the most unique and richest information and data (even much more so than the retina), and if it proves to be a viable biometric technology, it will far surpass the levels of the other biometrics which currently exist in the marketplace;
- Collectability: The right quality and quantity of DNA must be present, and the material must not be contaminated;
- Performance: DNA analysis is very useful and robust for forensic types of applications, but for verification purposes, it is still not useful, because the four to five hours of analysis which is required at present must be brought down to a matter of mere seconds;
- Acceptability: DNA is very much to prone privacy rights issues, and while the DNA profile itself does possess genetic information about an individual, the raw DNA data does have this;
- Resistance to Circumvention: Although DNA is rich in terms of data and information, it can often be very easily substituted for another person’s DNA.
Other disadvantages of DNA recognition include:
- DNA samples are prone to degradation and contaminants;
- Implementing the security protocols for a DNA-based biometric system could prove exceptionally complex. This applies to database protection and overall system confidentiality in equal measure.