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How Does a DNA Test Work?



Much beloved of TV talk show hosts like Maury, Dr. Phil, and Jerry Springer, DNA tests are more than fodder for trash TV – they can be a transformative undertaking for people confused and concerned about the biological identity of themselves or their children.

And although DNA tests were for a long time expensive and hard to obtain, in recent years genetic laboratories such as easyDNA have begun to provide efficient and confidential DNA tests at affordable prices.

Home testing kits have made it even easier to perform a DNA test – now you can take a genetic sample at home and send it to a laboratory for remote testing, and get the result via email.

Reasons for taking a DNA test vary. Often, they are used for paternity testing to determine the true father of a child, which can have important legal ramifications. You can also perform DNA health testing, help to establish a familial relationship between two suspected relatives, or uncover alleged infidelity.

On a happier note, DNA tests can be used to discover ancient ancestry, the gender of an unborn child, or even be turned into unique works of art.

Usually, DNA samples are collected by a simple cheek swab. This is nothing more than a cotton swab that is rubbed against the inside of the cheek and lip, as well as beneath the tongue to ensure a good collection of the skin cells that are naturally shed inside the mouth.

However, it’s also possible to collect samples more discreetly – although test results obtained from such samples are usually not legally certifiable. These discreet samples can range from bloodstains on tissue, to samples from cigarette butts, even right down to a licked stamp or toothpick.

However, the accuracy of results from such samples can vary wildly, so a cotton swab is usually the easiest and most accurate method.

The samples are then returned to a laboratory, where the science part comes in. The DNA is extracted from each sample and the separate strands – each containing hundreds or even thousands of genes – are split up into easily managed chunks. Then the work can begin creating a unique fingerprint from those chunks so that it can be compared against another sample.

Humans share 99.9% of our DNA, but that remaining 0.1% is a genetic fingerprint unique to each individual. By looking at the similarities and differences between the fingerprints obtained from two samples, geneticists can establish how closely the two samples are related – and therefore how closely the two individuals are related.

So the next time you watch the outcome of a hotly contested paternity test on TV, consider – just for a second – the enormous scientific research that went into finding that answer.