ALIGNMENT AND SENSITIVE DETECTION OF DNA BY A MOVING INTERFACE

In a process called ''molecular combing,'' DNA molecules attached at o ne end to a solid surface were extended and aligned by a receding air- water interface and left to dry on the surface. Molecular combing was observed to extend the length of the bacteriophage lambda DNA molecule to 21.5 +/- 0.5 micrometers (unextended length, 16.2 micrometers). Wi th the combing process, it was possible to (i) extend a chromosomal Es cherichia coli DNA fragment (10(6) base pairs) and (ii) detect a minut e quantity of DNA (10(3) molecules). These results open the way for a faster physical mapping of the genome and for the detection of small q uantities of target DNA from a population of molecules.