【摘要】 文章主要叙述了目前克隆新基因（ｃＤＮＡ）常用的几种方法——递减杂交，表达序列标记，ｍＲＮＡ差别显示，并对每种方法的原理，优缺点及应用情况作了简单介绍，以供有关研究者参考更多还原

【Abstract】 The human genome is estimated to consist of 100,000 genes,but the majority of human genes (about 95%) remains unknown.Since the end of the 1980’s a few of methods of searching for novel genes have been explored.Among them,subtractive hybridization,ESTs (Expressed Sequence Tags) and mRNA differential display are used more extensively. Subtractive hybridization is a method to search for gene expressed uniquely or preferentially in one of a pair of closely related cell population.In contrast to other methods,subtractive hybridization is a method specific in cancer research project.It is a method providing a positive selection procedure to screen for candidate oncogenes and tumor suppressor genes.ESTs is a method for partial sequencing of randomly selected clones with an average of 400bp from tissue specific cDNA libraries.Because ESTs is a method for cDNA sequencing,much valuable information from intronic and intergenic regions,including control and regulatory sequences,will be missed.mRNA differential display,a reverse transcription PCR (RT PCR) based approach,has opened up a wide avenue to study differential gene expression.As opposed to the use of the cDNA libraries,the major advantage of this approach is that the mRNA differential display permits analysis of gene expression during very narrow developmental windows.Because the mRNA differential display approach is optimized to generate cDNAs that are relatively small (100—500bp),the isolation and characterization of longer or full length cDNAs could be permitted by the combination this approach with the screening of cDNA libraries.更多还原