Biology Reference
In-Depth Information
by the mass spectrometer. Spiking samples with known amounts of an isotope
of the substance of which the quantity needs to be determined, therefore enables
quantitative determination of amounts of proteins (more often in relative terms
but occasionally absolutely (e.g. Beynon et al., 2005)).
The genome-wide determination of gene expression at the levels of mRNA
and protein are called transcriptomics and proteomics, respectively. Genome-wide
analysis of the expression at the level of metabolism, which is often closest to
function, is called metabolomics. Genome-wide metabolomics has not yet been
developed to the same extent as transcriptomics (Dunn, Bailey & Johnson, 2005;
Dunn & Ellis, 2005; Goodacre et al., 2004). Mass spectrometry methods akin
to the ones described above for proteins are being developed for metabolomics.
Again it is a problem to get the metabolites into the gas phase and to determine
their level quantitatively; isotope methodology can again solve this problem
(though one needs an isotope for each determinand, and the larger problem
resides in the fact that we do not know what most of these molecules are ).
Cell function is determined not only by the expression levels of proteins but
also by where they are expressed. Here three developments are highly important.
One is that of high-resolution microscopy. The second is the development of
many fluorescent probes for important molecules and ions in living cells. And
third is the possibility of fluorescence- or luminescence-based reporter proteins,
which are either fused to proteins of interest or are put under the control of the
gene-expression control elements that normally drive the expression of proteins
of interest. Thanks to these methodologies, the timing of expression and the
dynamic localization of many molecules in the living cell can now be determined.
Another less profound, yet highly important advance in technology is that of
robotization and automation for high throughput experimentation. By using plates
with many reaction vessels and robots doing the pipetting, many experiments
can be performed in parallel and at much enhanced reproducibility.
At present one can determine for all genes in a genome simultaneously whether
they are expressed at the level of mRNA. Soon this will also be possible at the
level of protein and in terms of their relationship to further levels of function-
ality, e.g. at the level of metabolites. Through functional genomics, therefore,
everything will potentially soon be knowable and known about living cells. For
unicellular organisms this should imply that everything will be known about a
living organism, albeit that collections of such cells remain highly heterogeneous
(Davey & Kell 1996). Every component can be manipulated by expressing the
corresponding gene in the organism under the control of a regulatory element
that can be steered by the experimenter. Everything will come to be known there-
fore and systems of Life will come under complete experimental control. The
limitations of the 'undefinedness' and inaccessibility to falsification-verification
experiments of biology, will soon be gone. Finally biology can stop collecting
stamps and become 'proper Physics', or so it would seem.
