As the human genome project is completed, microarray technology offers the potential to study the genomes complexity. This technology facilitates the direct extraction of functional information from nucleic acids by measuring the RNA levels of a complete organism or its associated subsets.
After isolation of total RNA, various methods can be applied to prepare
targets for microarray screening (Figure 1). The most common procedure
involves direct cDNA labeling by reverse transcription in which fluorescencelabeled
nucleotides are incorporated. A clear limitation of this technology is
the large amount of RNA required per hybridization. Some of the most important
applications in medical research involve studying very small amounts of
tissues (e.g., microdissected tissue [LCM] or biopsy material from tumors).
Therefore, target amplification methods have been developed to overcome