Bacteria have defences against viruses in the form of chemicals called restrictionenzymes, which chop up foreign DNA.
细菌有一种对病毒的防御机制:一种叫做限制性内切酶的化学物质可以切断外源dna。
2
The method USES fluorescence microscopy to image individual DNA molecules that have been divided into orderly fragments by so-called restrictionenzymes.