If you mention DNA most people think about fingerprints at a crime scene or testing for paternity. Genetic testing has become an accepted part of modern day life, but very few of us understand how it works.
In our lab it’s a cheek swab sample that becomes transformed into a report. So how does this happen?
The myDNA lab in housed in a relatively ordinary office building, but the machines inside it are far from ordinary. Manufactured in the USA, these PCR machines are the engines that drive the myDNA business.
Also flown in from the States, packed in dry ice, are arrays. They’re about the size of a thumb. They look like a miniature solar panel with thousands of tiny holes. Each of the 3000 pinprick holes in the array can measure one genetic variant in one person. Inside each hole are dried particles of chemical substances that become active when certain liquids are added.
Breaking the DNA cells open
Samples arrive by post at specimen reception. The lab scientists log all swabs using the barcode that’s placed on the tube during sample collection. This means that the sample can always be quickly and accurately identified.
The DNA is extracted from the swab using a substance called proteinase-K which breaks open the cells to release the DNA from the nucleus. Then the cells are incubated and broken open further. Next the lab scientists use magnetic bead extraction technology in which the DNA attaches to the magnetic particles, which allows it to go through a series of washes. At the end of that, the DNA is eluted (separated) from the magnetic particles. The result is purified DNA in a buffer solution. Got all that?
Expanding the DNA sequence
The DNA is then replicated, using a process called PCR (polymerase chain reaction). This means that the genetic material is copied several times over so that the lab can generate large enough quantities to analyse the genetic material.
The DNA sample and an enzyme called ‘taq polymerase’ are added to the open array. The array contains substances called primers. These are used to amplify and duplicate the DNA. A chemical probe that has fluorescence in it sits in the middle of the primers.
In a chemical process, the primers knock the probe off the strand of DNA causing fluorescence. Think of this as a tiny fireworks display. This happens 50 times. The process starts with one molecule and ends up with billions because the number of molecules doubles each time. The fluorescence is visualised as a graphical plot on a computer screen, which is used to identify an individual’s genetic results.
Explaining genetic mutations
The lab can also do a process called ‘copy number’ which can definitively prove if someone has an additional copy of a gene called CYP2D6 and how that additional gene functions.
Transforming the data into a report
All the results get transferred from the lab equipment to an encrypted secure database. This is where the relevant results are converted into a report and reviewed by our clinical team.
Why can it take up to 15 business days to get a myDNA report?
Analysis can take time for several reasons. Firstly, the lab relies on the postal system. Once the samples are received, logged and ready to go, extraction takes a day, and genotyping can take 2 days. Each tiny array costs $1000. It can only be used once. That means that testing needs to be batched in groups to make it cost effective.
The quality assurance processes to check the results also take a day. Sometimes follow up tests are needed to further check results. The lab scientists work extremely hard to ensure all results are accurate and verified and at times this can be time consuming.