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Since the eight reactions were run on fragments of random length, the eight plus and minus reactions collectively produced DNA fragments of all possible lengths.4 The fragments in these eight reactions were separated by size (using gel electrophoresis) and then imaged with autoradiography. Gels were dried and then placed against X-ray film, allowing the radioactive DNA fragments to expose the film and appear as dark bands, which a scientist could then painstakingly translate into the DNA sequence. In 1977, Sanger and colleagues sequenced the first full DNA genome using this method: a small bacterial virus with 5,386 nucleotides in its genome, called ɸX174 or “PhiX.”
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宫颈癌的核心诱因是HPV（人乳头瘤病毒）感染，但从感染到最终确诊宫颈癌并非一蹴而就，而是需经历明确的渐进式病变过程：首先是宫颈低级别鳞状上皮内病变（LSIL，即CIN1），随后进展为宫颈高级别鳞状上皮内病变（HSIL，含中度CIN2与重度CIN3）。临床数据显示，从HPV感染发展为宫颈癌前病变通常需要5年左右；而从癌前病变进一步恶化为浸润癌，周期可长达10至20年。