Not long after Arber's discoveries, Arthur Kornberg identified the pasting mechanism for DNA, an enzyme he called ligase.
Kornberg was trying to construct artificial viral DNA from viral fragments, but had been unable to make a biologically active molecule. Once he added ligase, however, he found that the enzyme made it possible to paste the ends of DNA molecules together.<br><br>
With ligase, the viral DNA he created formed a continuous loop, just as it did in the original virus. The artificial viral DNA was indeed biologically active, it could reproduce on its own, and Kornberg was hailed as having "made life in a test tube."
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Two sequencing techniques were developed independently in the 1970s. The method developed by Fred Sanger used chemically altered "dideoxy" bases to terminate newly synthesized DNA fragments at specific bases (either A, C, T, or G). These fragments are th