Nonradioactive Labeling and Detection of mRNAs Hybridized onto Nucleic Acid cDNA Arrays

Cellular gene expression changes during ontogenetic development of cell physiological activation-inhibtion and differentiation. Classical molecular assays like Southern, Northern, or Western blotting display only a few genes at once. The analysis of complex alterations of gene expression patterns, therefore, requires large quantities of biological materials, has significant experimental inter- and intravariability, and is quite time-consuming. Some of these problems became negligible with the advent of microarray techniques (1 ,2 ). cDNAs or oligonucleotids are immobilized on glass or membrane surfaces, cDNA or cRNA transcribed from cellular mRNA is hybridized, and signal detection is performed by radioactive or fluorescent techniques. The expression of up to several tens of thousands of genes can be made visible on small arrays, enabling investigators a rapid quantitative and qualitative analysis of pro- or eukaryotic gene expression patterns.