Out of the Blue

GenomicsOne's TrueBlue Cloning Scheme For the past two decades, cloners have relied on lacZ*-based color selection vectors to identify cloned inserts. These systems are based on the insertional inactivation of the lacZ* gene fragment and are (deceptively) simple. The lacZ gene encodes the ß-galactosidase (ßGal) protein, which acts on an indicator substrate to produce blue colonies. Thus, in a cloning experiment, white colonies indicate that the DNA of interest has been inserted into t

Aileen Constans

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GenomicsOne's TrueBlue Cloning Scheme

For the past two decades, cloners have relied on lacZ*-based color selection vectors to identify cloned inserts. These systems are based on the insertional inactivation of the lacZ* gene fragment and are (deceptively) simple. The lacZ gene encodes the ß-galactosidase (ßGal) protein, which acts on an indicator substrate to produce blue colonies. Thus, in a cloning experiment, white colonies indicate that the DNA of interest has been inserted into the lacZ* coding region of the vector, disrupting ßGal expression, while blue colonies indicate that lacZ is intact and insertion has not occurred. However, many blue-white screeners find that this color selection method can be quite inaccurate, and one study found that approximately 30-40 percent of blue colonies actually contained inserts.¹GenomicsOne Corp. of Montreal has come to the rescue with its TrueBlue Technology, which provides a highly reliable blue-white selection procedure.

False negatives can occur when ...

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