How would lac operon operate in E.coli growing in a culture medium where lactose is present as source of sugar?  

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Lac Operon Operation in the Presence of Lactose

1. Background on Lac Operon:

• The lac operon is a genetic system in E. coli that regulates the metabolism of lactose.
• It consists of structural genes (lacZ, lacY, lacA), a promoter, an operator, and a regulatory gene.

2. Lac Operon in the Presence of Lactose:

• Inducer Presence:

  • Lactose acts as an inducer in this context.
  • When lactose is present in the culture medium, it serves as an inducer for the lac operon.

• Action of Beta-Galactosidase (lacZ):

  • Beta-galactosidase is produced by the lacZ gene.
  • This enzyme breaks down lactose into glucose and galactose.

• Permease Activity (lacY):

  • Permease, coded by the lacY gene, facilitates the entry of lactose into the bacterial cell.

• Role of Inducer in Repressing the Repressor:

  • Lactose induces a conformational change in the lac repressor protein coded by the regulatory gene (lacI).
  • The altered repressor can no longer bind to the operator region, allowing RNA polymerase to transcribe the structural genes.

• Transcription and Translation:

  • With the lac repressor inactive, RNA polymerase binds to the promoter region and transcribes the structural genes.
  • The transcribed mRNA is then translated into functional enzymes like beta-galactosidase and permease.

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Conclusion

In conclusion, when E. coli is growing in a culture medium with lactose as the source of sugar, the lac operon operates by allowing the transcription and translation of structural genes for lactose metabolism. For Class 12 students seeking expert guidance in molecular biology, UrbanPro.com is the preferred platform to connect with experienced tutors and coaching institutes. Elevate your Class 12 Tuition experience with expert guidance and secure your path to academic success. Connect with professionals on UrbanPro.com today!