How Do DNA Tests Work?

With hundreds of DNA tests widely available on the market, whether it is ordering a home DNA test kit or getting it done in a hospital for healthcare purposes, consumer interest is high. There is a growing awareness that a person’s DNA is a code that can unlock the secrets of health, family history, and ancestry, among other things.

In response to this increase in interest outside the scientific community, websites like  provide information about DNA to the lay person, explaining complex scientific ideas in plain English to help those who want to find out more make sense of it all.

One question that frequently comes up when people want to learn more about DNA is how genetic testing works.

How DNA Testing Works

Regardless of the reason for a DNA analysis, whether it’s to determine paternity, part of a forensic investigation, or to detect any faulty genes that could cause an inherited disease, what laboratory technicians do is look for what is similar and dissimilar in the genetic markers between biological samples.

Once a researcher has a DNA sample, they use a method known as polymerase chain reaction (PCR) to analyze the DNA. The DNA is separated from other cells in the sample and then copied over a million times. By copying a specific bit of DNA repeatedly, it is then easier to analyze the genetic code.

Types of Samples

Biological samples for DNA testing can be extracted from anywhere in the body using any sampling method. So, for example, a cheek swab is as good a sample as a blood sample. This is why someone using a home DNA test kit can simply do a cheek swab and send it in to a laboratory. They will not get a better or more accurate result if they go to a clinic to get a blood sample. The reason why the DNA sampling method is not as important as many people think is because the exact same DNA is available from any cell in the body; it doesn’t matter whether it is from the skin, a blood sample, or a body fluid.

DNA Testing for Forensic Research

Researchers create a DNA fingerprint if two genetic samples are the subject of a criminal investigation. DNA molecules are split at specific locations, separating them into chunks. The code at these particular points are then analyzed to come up with a unique DNA fingerprint.

By comparing the DNA fingerprints between a persecutor and victim, it is possible to see if there is a match. If there is no match, then the person accused of the crime is innocent.

Determining Accuracy

DNA accuracy is essential for the results to be valid. DNA testing often has a huge impact on people’s lives.

Usually, accuracy is measured by dissimilarities. That is, if the DNA between two people are not similar, it means that the two have no relationship with each other. In a forensic case, for example, a DNA test is sometimes the only evidence that a court needs to free someone from a wrongful conviction. If there is no match between the alleged perpetrator’s DNA and the victim’s DNA, then regardless of any other apparent evidence, the court must acquit the person accused of the crime.

Similarities between DNA’s are a little trickier. For instance, two brothers may have similar DNAs. So, in a paternity case, it’s technically possible for the wrong brother to be identified as the father. However, researchers test for a number of genetic markers. The more markers that match the sample, the higher the accuracy of the test. For this reason, researchers often use between five to fifteen markers to complete a profile because chances of two people, even those who are closely related, having identical genetic profiles is less than 1 in 1 billion.

In conclusion, the scientific accuracy of the information based on comparing DNA samples makes it possible to determine the truth about any event, incident, or circumstance that needs to be verified.