The completion of the Human Genome Project has made possible the comprehensive analysis of gene expression using DNA microarrays. A limiting factor for these studies is the amount of RNA available, particularly if the sample is derived from a surgical specimen. In this issue, Marincola and colleagues ( p. 457) have devised a procedure that optimizes amplification of low abundance RNA samples by combining the template switching effect with antisense RNA amplification. Their results define the operational parameters of RNA amplification and should facilitate the use of DNA microarrays for applications where starting material is limiting, such as clinical samples from fine-needle aspirates or microdissection.

Chemical mutagenesis has not been used widely for reverse genetic strategies for the analysis of gene function due to the difficulty in detecting lesions, which are primarily point mutations. In this issue, McCallum et al. (p. 455) demonstrate that mutations induced by ethyl methanesulfonate (EMS) in Aridopsis thaliana can be easily identified by a denaturing high-performance liquid chromatography (DHPLC) single nucleotide point mutations by heteroduplex analysis. The method is efficient and automatable and should be applicable to any organism that can be chemically mutagenized.