Genes, Brains, and Human Potential The Science and Ideology of Intelligence

124 REAL GENES, REAL INTELLIGENCE

TFs are considered to form the rather deterministic gene regulatory
networks mentioned in chapter 1. But they do not function as in de pen-
dent units. As Sara Berthoumieux and colleagues note from their experi-
ments, the transcriptional response of the network is itself controlled by
the physiological state of the cell. Accordingly, “the absence of a strong
regulatory eff ect of transcription factors suggests that they are not the
main coordinators of gene expression changes during growth transi-
tions.” Instead it is appropriate to regard them “as complementing and
fi ne tuning the global control exerted by the physiological state of the
cell.”^17 Th is change of perspective, they point out, has impor tant conse-
quences for the interpretation of so- called gene networks. In addition,
TFs themselves interact, some serving as co- repressors or co- activators
of other TFs, with some TFs regulating other TFs (again the term “orches-
tration” is sometimes used).
In other words, the whole is a vast self- organ izing control network
involving feed- forward and feedback loops. TF recruitment depends on
the resolutions of signaling networks, which are shaped by input from
signaling receptors, that register the structure of changing environmen-
tal patterns. Computer models demonstrate that such systems have tre-
mendous powers of control and creativity of response.

Using the Genes

As already mentioned, TFs do not work alone but with a variety of pro-

moters, enhancers, and co- activators. Together with other factors, they

recruit RNA polymerase. Th is is the enzyme that attaches to the DNA

and copies the sequence into messenger RNA (mRNA). It is actually the

mRNA that serves as the sequence template bringing amino acids to-

gether to form peptides and proteins. Imagine how all of these, too, are

products of gene transcription under the control of the signaling maze,

and you begin to get a picture of how interactive the entire pro cess is.

Already we can see that there is no single command level, no single

dominant factor in charge, but a self- organ izing global pattern formed

among myriad components responding to environmental changes.

Together these factors vastly expand the transcriptome— that is, ways in

which the network responds and genes are utilized, according to con-

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