Lac Operon: Advanced Look --> 2.) Expression

Once the repressor has been released, expression of the lac genes can take place. In order to express the genes they must first be transcribed and then translated. This section outlines the transcription and translation of the two genes being illustrated: Z and Y. Clicking on each of the thumbnail images will bring up a larger, labeled version of the described scene.

To see the Quicktime movie for the following sequence of images, click here.

	Once the repressor has been released, RNA polymerase can bind to the DNA and begin transcription.
	The mRNA that is produced consists of three domains, complementing the genes on the DNA.
	Each of the three domains on the newly made mRNA corresponds to a different protein. Only the role of the first two will be studied here.
	Now the small and large subunits of the ribosomes can bind to the mRNA. Here translation of the first protein, ß-galactosidase, has begun.
	Now both ß-galactosidase (orange) and the second protein, permease (yellow), are being translated. It should be noted that in prokaryotic cells more than one ribosome may be attached to the mRNA at the same time.
	After being successfully translated, permease becomes embedded in the membrane of the cell.

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