From blood to DNA

My name’s Aamisha Kyada, and I’m an assistant genetic technologist in a genetics laboratory. I’m going to show you how we extract DNA from a blood sample. The blood sample’s in a tube containing EDTA to stop the blood from clotting in the tube. This is what the DNA looks like.

When a blood sample arrives in the lab, we check that the patient’s identifying details on the blood tube match those on the request form, and then record the patient’s name, date of birth, and NHS number on the lab database. A unique barcode is printed and stuck on to the blood tubes so that we can track the sample through every stage of the testing process to ensure that correct result is issued for that patient. We extract DNA from blood samples using an automated DNA extraction robot. The separation of DNA is achieved through capture onto magnetic beads, which are then attracted to metal rods magnetized by an electromagnet. The magnetic rods transfer DNA-bound magnetic beads through a series of different wash buffers.

In the first step, the rods take up sheath to prevent cross-contamination between the patient samples. The next step is to break open cells to release the DNA that’s located inside the white blood cells. We use a lysis buffer to break open the cells and a protease enyzme to remove proteins from our blood samples. The magnetic rods are rotated to mix the solution. Magnetic beads and a binding solution are then added to the sample to bind the DNA. After binding, the electromagnet is switched on, and the DNA bound to the beads is attracted to the rods. The DNA undergoes a series of washes to remove any impurities and inhibitors that might affect the next stage of the genetic testing process.

After removing the last traces of wash buffer, the DNA-bound bead pellet is resuspended in elution buffer to release the purified DNA from the beads. The last step is to transfer the DNA into barcode label tubes. Once we measure the amount of DNA and check that it meets our quality standard, we are ready to start the genetic test.