LacZα gene

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The LacZα gene is one of the structural genes present on the Lac Operon in Escherichia coli bacteria[1]. When transcribed by RNA polymerase, the LacZα gene codes for β-galactosidase, an enzyme responsible for the hydrolysis of β-galactosides (e.g. lactose)[2][3]. On the lac operon, the LacZα gene exists between the operator region and the LacY gene[4].

The LacZα gene is only transcribed in certain conditions. Lactose must be present when glucose is unavailable due to the presence of a repressor protein (Lac repressor) on the operator region of the Lac Operon[5]. This repressor protein prevents RNA polymerase from binding to the operator region; hence transcription of the structural genes cannot take place.

Fragments of the LacZα gene are also used in the recombinant DNA technologies to identify recombinant plasmids (a plasmid with a new section of DNA added) in bacterial colonies. New genes are inserted into the multiple cloning site (MCS), which lies in a region of the LacZα gene fragment. Therefore, recombinant bacteria produce β-galactosidase (as the LacZα gene is not disrupted), whereas the non-recombinant bacteria do not (as the LacZα gene is disrupted, therefore inactive). Hence, due to the LacZα gene, recombinant bacteria can be easily detected[6].

References

  1. Hartl, D.L., Ruvolo, M. 2012. Genetics: Analysis of Genes and Genomes, Eighth Edition. Burlington, MA: Jones & Bartlett Learning. Page 394.
  2. Kalnins, A et al. 1983. Sequence of the lacZ gene of Escherichia coli. The EMBO Journal, 2,4, 593-597.
  3. Hartl, D.L., Ruvolo, M. 2012. Genetics: Analysis of Genes and Genomes, Eighth Edition. Burlington, MA: Jones & Bartlett Learning. Page 391.
  4. Hardin, J. et al. 2012. Becker's World of the Cell, Eighth Edition. Boston, MA: Benjamin Cummings. Page 712.
  5. Hardin, J. et al. 2012. Becker's World of the Cell, Eighth Edition. Boston, MA: Benjamin Cummings. Page 713.
  6. Hartl, D.L., Ruvolo, M. 2012. Genetics: Analysis of Genes and Genomes, Eighth Edition. Burlington, MA: Jones & Bartlett Learning. Page 450.
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