How do DNA databases work?

DNA (deoxyribonucleic acid) databases or data banks are basically management systems for the storage of genetic data. This data is collected from thousands, if not millions, of people and can be used for several purposes, including genetic research, genetic fingerprinting and crime solving. Different countries have different laws and regulations regarding the collection of DNA, access to the DNA banks, the length of time that any DNA profile is retained and other related issues.

DNA databases and forensic DNA analysis have proved a turning point in solving crimes and also, importantly, in exonerating people who might otherwise have been found guilty of or implicated in crimes they were actually innocent of committing. Any DNA found at a crime scene can be run against the thousands of profiles in the database to find a match, thereby finding the culprit, or at least a suspect.

A DNA profile is essentially a partial map of a genetic pattern. Many private DNA testing companies, such as homeDNAdirect, offer DNA profiling services; however, these are aimed at private individuals and entities and may differ from the profiles stored in government databases.

Where are DNA databases held?

By virtue of their importance, DNA databases are usually maintained by government institutions, important private organisations, universities, genetic laboratories and police departments. Despite their name, however, many DNA databases only hold DNA for a very brief span of time. The raw data gathered from actual DNA is used to create DNA profiles, which are then stored in the DNA database. Once that is done, the DNA samples themselves are normally either destroyed or stored.

The UK National DNA Database

The UK DNA database (officially the UK National Criminal Intelligence DNA Database; known by the acronym NDNAD) was set up back in 1995 and contains solely DNA profiles collected at crime scenes - this database contains the DNA profiles of around 5.2 per cent of the UK's population. Samples from convicted criminals and any person charged with an offence are held in the database - interestingly, samples are retained even if the person is acquitted of a crime, although the Protection of Freedoms Act has decreed that many of the DNA profiles of innocent people should be destroyed. Scotland has its own database and differs from the UK database in that profiles of acquitted individuals are not retained. The Scottish database exports copies of its own DNA data into the UK database.

The NDNAD profiles map a given number of genetic markers per individual. Due to the fact that these profiles only map a fixed number of markers, they cannot give access to the full genome - this is an important point as it limits the amount of information a person can access by analysing the DNA profile in question. The database also contains and preserves forensic sample specimens such as hair, skin or blood. Such samples can be used to yield more genetic information, such as disease susceptibility, to derive clues about one's ancestral origins or to find familial links.

Another important DNA database is the Combined DNA Index System (CODIS), which is funded and supported by the FBI. This database is used for storing DNA profiles from federal, state and local crime labs from all over the United States. Because of its affiliation with the FBI, CODIS is used primarily for tracking crime suspects and aiding law enforcement agencies in their investigations.

Other large and important DNA databases can be found in Australia and Canada. Like CODIS, these databases are used for law enforcement purposes. However, there are also important DNA databases which are not used for criminal investigation: numerous databases have been established to serve research and public demand for DNA information.

Issues and controversy with DNA databases

In order to understand how a DNA database is created and developed, it's important to review certain facts about DNA. DNA (or deoxyribonucleic acid) contains the unique genetic information of each living being. It can be extracted from our blood, semen, saliva or any type of tissue from the human body. The information found in your DNA is unique and can be used to offer interesting information about your genealogy, current health and even your medical background. Government databases have created much controversy because of the personal information they provide and the unease often voiced over the possibility of accessing a person's genetic information once it is stored in the database. In the UK, genetic research has been conducted using the genetic material found in the national database. The extent to which the database is controlled and regulated is not apparent from every possible area of scrutiny and concerns have been put forward by groups such as GeneWatch, a not-for-profit organisation that monitors developments in genetic technologies.

Moreover, further issues arise because, while we all know that DNA is a powerful tool for discriminating between two individuals and that everyone's DNA profile is unique, when running a comparison between a DNA sample found at a crime scene and the DNA profiles stored in a database, close matches may be singled out. Matches indicate a high probability but not absolute certainty, which means that people with a very similar DNA profile to that found at the crime scene may find themselves roped into the investigation or even singled out as suspects. This often happens with close relatives who have a lot of DNA in common.

Sarah White specialises in the field of DNA and Genetics