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asthma, for example. This is because they would seal the lungs because the beta2 receptors

that keep the airways clear would then be blocked. So often the side effects of a drug come

from other receptors besides the intended receptor being hit and blocked by the drug.

However, when I measure gene expression, I only see the side effects if I also measure in

a tissue where such side effects come into play. For example, especially in the lungs, but

also in other tissues where beta2-receptors are present, these effects would cause the

receptors to be less active, again changing numerous genes.

Of course, one can still more generally require that the main effect only fixes exactly

the defect (causal therapy) and does not change anything else (no side effect). But this is

not the case for most drugs because the body is too complex. A good example is diabetes

treatment (diabetes mellitus, diabetes) by insulin. Actually, this is exactly the substance

that the diabetic lacks. But since even insulin pumps cannot control insulin as precisely as

the healthy body can with the help of the pancreas, the sick person has to deal with many

small over- and underdoses of insulin all the time and in every cell of the body at

the moment.

Bioinformatics can therefore be used to effectively evaluate the large amounts of data

(DNA: so-called genomics, RNA: so-called transcriptomics, proteins: so-called pro­

teomics, metabolism: so-called metabolomics) that describe in detail how biological sys­

tems react to drugs or environmental influences. There are fundamental limits to the

short-term exact describability that apply to all systems controlled with feedback loops,

such as living cells or even our weather. Therefore, it is important to know the range to

which such systems are set and into which they always fall back, the attractors of the sys­

tem. You have already learned about these in Sect. 5.1. There we introduced them simply

as “stable system states”. Stewart Kaufmann is an important researcher and founder of

system sciences who has described natural and biological systems in general terms.

9.2

Opening Up Complex Systems Using Omics Techniques

9.2

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9.1

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Genome sequencing using ultrafast sequencing technologies, such as the 454 or Solexa

technology, is now a common method that enables the rapid and cost-effective sequencing

and annotation of genomes (nucleotide sequence in DNA). The ever-improving sequenc­

ing technologies also allow for increasingly high-resolution sequencing, which means that

newer and newer genes can be annotated. Numerous genomic data are accessible through

9.2  Opening Up Complex Systems Using Omics Techniques