The Science of DNA Testing

Wondering about how DNA testing works? Read on!

Casey Randall Alphabiolabs

By Casey Randall, Head of Genetics at AlphaBiolabs
Last reviewed: 05/19/2023

AlphaBiolabs Testing Procedure

AlphaBiolabs use cutting-edge technology to provide you with the fastest, most accurate and cost-effective DNA testing process available. Our general procedure is to take the DNA cell sample with a cheek swab and then process it with the latest DNA profiling methods.

Our DNA testing process consists of five steps:

  • Sample collection
  • DNA extraction
  • Polymerase chain reaction (PCR)
  • Fragment analysis
  • Reporting

Collecting the sample

AlphaBiolabs uses cheek (buccal) cell samples for DNA relationship testing. They are easy to collect, non-invasive and painless.

Collecting the sample is crucial to the procedure since it is how the laboratory gets information on the test participants; if a sample is not taken correctly, it can cause delays in obtaining the results.

Peace of mind DNA testing is for your own knowledge, and the samples can be collected and provided by the donors themselves. This kind of testing is based on the information given by the participants and cannot be used for any legal purposes, such as changing a birth certificate.

The laboratory process

Upon arrival at AlphaBiolabs, the cells in the sample are broken open and DNA is separated from other parts of the cell. We use cutting-edge extraction techniques to process the cells to ensure the highest level of accuracy and purest quality sample.

Once the high-quality DNA samples are extracted, we subject them to Polymerase Chain Reaction (PCR). PCR is a biochemical technology that captures the cell’s ability to replicate DNA, allowing for the generation of thousands to millions of copies of a particular DNA sequence.

Short Tandem Repeat (STR) markers are stretches of DNA with repeat sequences; each marker contains a DNA repeat. STR markers are found in various sizes, and we classify them by the length of core repeat units, the number of repeat units, as well as the overall length of the region of repeats.

AlphaBiolabs is one of just a few laboratories accredited to test up to 45 DNA STR markers in standard tests; most relationship tests examine only 16 STR markers.

Read more about DNA STR markers

An allele is one of a pair of genes that appear at a particular location on a particular chromosome and variations in alleles is what allows us to perform relationship testing.

The PCR technique allows for easy amplification of STRs without having the problem of differential amplification. In other words, the millions of STRs produced through PCR are generally similar in profile, making them especially suitable for human identification.

Because they are smaller, it is easier to separate STR alleles from other chromosomal locations. It is essential to avoid choosing closely linked locations since they do not follow the predictable pattern of random distribution in the population; this might make statistical analysis difficult. A person inherits one copy of an STR from each parent, which may or may not have similar repeat sizes. Although much of our DNA is identical to other people, the STR markers are inherited regions of our DNA that can vary from individual to individual. This makes the STR markers effective for human identification.

For the purpose of relationship testing, it is important that we have DNA markers that show the highest possible variation in order to discriminate between samples. AlphaBiolabs’ PCR procedure specifically targets up to 45 STR markers within the genome (an individual’s total DNA). Highly differentiated STR markers allow the PCR process to generate results providing as much information as possible to provide a conclusive result.

AlphaBiolabs uses a Genetic Analyzer to examine the products of the PCR technique to determine the number of repeats at each STR location. This separates the DNA fragments by size, building a DNA footprint of the sample donor. These profiles can then be used for human identification and relationship analysis, such as paternity and sibling testing.

For paternity testing, we compare the STR markers seen in the child with those seen in the parents. As a child inherits 50% of its DNA from each parent, the inherited DNA includes the STR markers found on the parents’ chromosomes. The child will then show a unique combination of DNA from his or her parents.

Order a Home DNA Paternity Test Online

In AlphaBiolabs paternity DNA tests, we compare each STR marker to identify the alleles that have been inherited. We then can calculate a Paternity Index (PI), the statistical strength or weight of that marker in favor of, or against, parentage. Next, we multiply the PI for each marker to create the Combined Paternity Index (CPI): the higher the CPI, the more likely that the parents are the true biological parents of the tested child.

The CPI value is used to create the Probability of Paternity. For a man to be confirmed as the true biological father, the Probability of Paternity must be greater than 99.99%. If the tested man has several STR markers that do not match the child’s profile, he is ruled out as the true biological father.

Relationship DNA tests are performed by comparing the DNA profiles for a group of individuals and considering the probability of any potential relationships.


Casey Randall AlphaBiolabs

Casey Randall

Head of Genetics at AlphaBiolabs
Casey joined AlphaBiolabs in 2012 and heads up both the Genetics and Health testing teams. An expert in DNA analysis and a member of the International Society for Forensic Genetics (ISFG), Casey holds an MS degree in DNA Profiling and a BS degree in Forensic Science. Casey is responsible for maintaining the highest quality testing standards, as well as looking for ways to further enhance the service that AlphaBiolabs provides and exploring new and innovative techniques in DNA analysis.

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