Blood samples thawing prior to DNA preparation.
© Science Museum / Science & Society Picture Library
Blood samples thawing prior to DNA preparation, Great Ormond Street Hospital, May 2000. Red blood cells do not contain DNA as they lose their nucleii (the compartment in a cell that contains the DNA) as they mature. Blood DNA is contained in the white blood cells. To extract it, a small sample of blood is spun at high speed to separate the cells from the blood fluid. Next, the DNA is released from the cells using a detergent and a special enzyme. Finally, alcohol is added, which makes the DNA appear as a sticky blob in the mixture.