第1个回答 2010-07-16
假阴性。我们分子考过的。
蓝斑中,可能插入了片段,插入的片段可能只是是目的片段的一小部分(被核酸酶不小心降解了),但由于插入的片段size很小,而且恰巧与lacZ基因的开放阅读框ORF(open reading frame)一样的话,就可能产生拥有部分活性的β-半乳糖苷酶β-lacZ,从而出现蓝斑。
False negative , that is, blue colonies with very short inserts. The inserted fragment is part of the whole insert, which may be degraded by nuclease into small inserts. Because the insert is too small, and it may use the same ORF as the origin LacZ, the result is a partly active enzyme which results in blue colonies.