The following images attempt to illustrate
how the lac operon gene sequence is expressed, and emphasize
some of its most important steps. Clicking on each of the
thumbnail images will bring up a larger, labeled version of the
see the Flash movie for the following sequence of images,
A simplified E.
coli bacterial cell.
The lac operon
The repressor molecule,
bound to the controlling region.
added to the enviroment outside of the cell.
bound to the repressor. This releases
the repressor from the DNA.
transcribing the genes in the lac operon into
the mRNA into proteins.
One of the proteins (yellow) encoded by the
lac operon allows lactose
to enter the cell at a high rate.
A second protein (orange) digests the lactose
as it enters the cell.
The lactose molecules
bound to the repressor are released.
binds to the controlling region of