<p>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</p> <p>Historically genotypic variation has been detected at the phenotypic level, at the metabolic
level, and at the protein chemistry level. Advances in technology have allowed its direct
visualisation at the level of DNA variation. Nevertheless, there is still an enormous interest
in phenotypic, metabolic and protein property variability, since such variation gives
insights into potential functionally important differences conferred by genetic variation.
High-throughput transcriptomics and proteomics applied to different individuals drawn
from a population has the potential to identify the functional consequences of genetic
variability, in terms of either differences in expression of mRNA or in terms of differences
in the quantities, pI(s) or molecular weight(s) of an expressed protein. Family studies can
define the genetic component of such variation (segregation analysis) and with the genotyping
of well-spaced markers can map the causative factors to broad chromosomal regions
(linkage analysis). Association studies in the variant proteins have the greatest power to
confirm the presence of <italic>cis</italic>-acting genetic variants. The most powerful study designs may
combine elements of both family and association studies applied to proteomic and
transcriptomic analyses. Such studies may provide appreciable advances in our understanding
of the genetic aetiology of complex disorders.</p>
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Comp Funct Genomics. 2002 Feb; 3(1):22-27