By raiding nature's tool cabinet, researchers have developed a potentially faster and more practical version of the polymerase chain reaction (PCR), itself a foundation of modern genetics.
The breakthrough, called helicase-dependent amplification (HDA), could result in small, hand-held devices which enable doctors to test blood samples directly in the surgery and forensic teams to detect a suspect's DNA at a crime scene. ...
But it [PCR] remains cumbersome and time-consuming because of the need to uncoil double-stranded DNA with heat. To make multiple copies of a target strand of DNA, the sample has to be repeatedly heated up to break the DNA, then cooled to allow more to form. But this "thermal recycling" requires energy, time and equipment that can only be used in a lab setting.
HDA could be about to change that because it relies on a technique which uncoils DNA the way nature does - with enzymes called helicases. ...
As with conventional PCR, Kong had to add "primers", slugs of DNA which bind to pre-selected target sequences in the uncoiled target strands, and which serve as the starting point for the strand to be copied. He also had to add polymerase, the enzyme which actually copies the strands.
In conventional PCR, newly formed strands recombine with each other to re-form DNA, which then has to be uncoiled again by raising the temperature to allow yet more to be made. But the helicase does the job instead, without reheating.
Monday, July 12, 2004
Freeze! Drop your weapon!
Get down on the ground and give me a blood sample NOW!