ABSTRACT
Cells need to adopt quickly to changes in their environment.
This often means that they either have to start or to stop the
production of certain proteins within a very short period of time.
Transcriptional regulation involves typically transcription factors,
DNA-binding proteins, that bind to their specific, a few bp long target
site. These proteins are either activators that are needed to switch
on transcription or repressors that switch it off. We will not discuss
here the rather involved transcriptional regulation inside eukaryotic
cells that typically involves a large number of proteins. Instead
we restrict ourselves to the much more simple regulation inside
bacteria. As mentioned in Section 1.2 such cells have no nucleus and
no chromatin. The presence of various repressors is crucial since a
bacterium needs at any given time only a fraction of the proteins that
are encoded in its genome.
