Unsupervised Clustering Analysis of Gene Expression

The availability of whole genome sequence data has facilitated the development of high-throughput technologies for monitoring biological signals on a genomic scale. The revolutionary microarray technology, first introduced in 1995 (Schena et al., 1995), is now one of the most valuable techniques for global gene expression profiling. Other high-throughput genomic technologies, such as Serial Analysis of Gene Expression (SAGE) (Velculescu et al., 1995), mass spectrometry for protein identification (Henzel et al., 1993) and ChIP-chip for DNA binding (Ren et al., 2000), have also been widely used for different purposes in current biological and medical research.