  This work analyses the transcriptional effects of some biochemical mechanisms
proposed in previous literature which attempts to explain the differential
spatial expression of Hedgehog target genes involved in Drosophila development.
Specifically, the expression of decapentaplegic and patched, genes whose
transcription is believed to be controlled by the activator and repressor forms
of the transcription factor Cubitus interruptus (Ci). This study is based on a
thermodynamic approach which provides binding equilibrium weighted average rate
expressions for genes controlled by transcription factors competing and
(possibly) cooperating for common binding sites, in the same way that Ci's
activator and repressor forms might do. These expressions are refined to
produce simpler equivalent formulae allowing their mathematical analysis.
Thanks to this, we can evaluate the correlation between several molecular
processes and biological features observed at tissular level. In particular, we
will focus on how high/low/differential affinity and null/total/partial
cooperation modify the activation/repression regions of the target genes or
provoke signal modulation.
