Question

DNA lac) laco lace lace Describe why the scientists used amount of b-galactosidase protein as a way to measure the activity of these genes? Limit response to 40 words maximum. HTML Editor B IV A - A - IE 3 1 1 1 x x := N VE You CV 6] | [ 12pt E Para

Answer 1

• Lac operon includes:

1.Promoter- Region for binding of RNA polymerase to initiate transcription of the structural genes present down-stream of the promoter.

1. Operator- Region where the repressor binds
2. Structural genes- Lac Z- encodes Beta galactosidase. Lac Y- encodes permease, Lac A- encodes transacetylase.
3. Lac i- represents encoding gene. The repressor and is under a separate promoter and not under lac promoter control.

• LAC operon of E. coli is an example of inducible gene expression system.
• Lactose acts as inducer molecule in lac operon.
• In absence of lactose (inducer) repressor binds to the operator region and prevents transcription of structural genes by RNA polymerase.
• Lactose binding to repressor, prevents it to bind to the operon and induces expression of structural genes.
• Thus, enzymes produced lac A and lac Y allows lactose in cell.
• Beta galactosidase enzyme break down lactose for use.
• Thus, the enzyme beta-galactosidase assay measures the inactivation of repressor by lac i, Lac Y and lac A expression which allows lactose to enter the cell and lac Z activity, which produce beta galactosidase.
• Beta-galactosidase assay may be easily conducted by measuring lactose conversion.
• Visual effect may be obtained bt formation of blue colonies on plates with IPTG and X-gal.