86

Next, one can compare the quality of different signal sources: For example, the infor­

mation value is very low if the same character is always sent, but very high if very different

characters are always sent in a new sequence, such as a radio station.

After all, you have to take into account what it looks like inside living cells: Countless

reactions take place, there is a lot of hustle and bustle. Therefore, biological signals are

often amplified in signal cascades, so that one can still understand the signal despite the

“noise” (all the other reactions and signals taking place). The quality of the signal depends

on the ratio of signal to background noise (signal-to-noise). Shannon has set up a whole

theory on how communication via communication channels can run as optimally as pos­

sible despite interference.

If the bioinformatician wants to model and better understand cell growth, differentia­

tion or the death of cells, these theories are taken into account and the amplification,

weakening and modelling of cellular signals in different signalling cascades is investi­

gated, as well as the weakening of kinase cascades by phosphatases, for example, so that

the cell stops growing again. At this complex level (function of the various signalling

cascades in the cell), a deeper understanding of the processes surrounding cell growth and

cell differentiation is then indeed possible.

7.2

The Different Levels of Coding

7  How to Better Understand Signal Cascades and Measure the Encoded Information