ABSTRACT
Rapid progress in the field of functional genomics has made it possible to monitor the expression of thousands of genes simultaneously. This chapter provides an overview of the principles and techniques of expression arrays, with particular emphasis on the use of cDNA expression microarrays. Microarrays can be produced using either oligonucleotide or cDNA representations of the genes. Although the type of expression data obtained is equivalent, there are important distinctions between the two methods with respect to their manufacture. cDNA microarrays are produced by spotting PCR-amplified cDNAs onto glass slides. cDNAs represent a much more complex hybridization substrate than oligonucleotides. Although carefully designed amplicons could be generated, in practice cDNAs are amplified from libraries of clones. The first stage in a microarray experiment involves the preparation of cDNAs and their arraying onto glass slides. A key advantage of the microarray format is the low reaction volumes required for hybridization, making it possible to use concentrated probe.
