5.1 Bio-Ontologies 97
identified a total of 1559 genes that have significantly different expression
patterns between the cases and controls using thet-test at significance level
0.05. This is still a very large number of genes to examine. To focus more
precisely on the genes that are most likely to be of importance in PTD, we se-
lected the genes that have been classified as being involved in the “response
to external stimulus” GO term of the GO biological process ontology. By
using the GO clustering tool of the DNA-Chip Analyzerwww.dchip.org
software, we found 159 genes belonging to this category. The gene expres-
sion profile is shown in figure 5.3.
Figure 5.3 A gene expression profiling study of preterm delivery (PTD) of eight
mothers with PTDs and six mothers with term deliveries. In this study, 159 genes
were found to be significantly belonging to the “Response to External Stimulus” GO
term (P<.0001).
A number of efforts are underway to enhance and extend GO. The Gene
Ontology Annotation (GOA), run by the European Bioinformatics Institute
(EBI), is providing assignments of terms from the GO resource to gene prod-