中文摘要：

靶向富集技术具有良好的均一性、特异性和灵敏性,只需较低的测序覆盖度即可满足后续的分析。该技术被广泛应用于特定位点重测序和染色体构象等研究。为了靶向富集测序文库中特定的染色体DNA片段,本研究以21号染色体为例,采用人胚肝二倍体细胞CCC-HEL-1建立了一种单染色体靶向富集方法。具体步骤如下：（1）首先将人正常核型二倍体细胞同步化到G2/M期,制备染色体悬液;然后流式分选出21号单染色体。（2）采用多重退火环形扩增技术（MALBAC）对21号染色体DNA进行扩增;用扩增的DNA产物构建文库。（3）利用体外转录合成、生物素标记的RNA探针与文库进行液相杂交,捕获并验证捕获效率。荧光定量PCR检测结果证明,特定的21号染色体呈上百倍的富集,而靶标文库则富集了近60倍。结果提示,特异单染色体靶向富集方法成功建立。该法不仅可实现任一单染色体的靶向富集,用于单条染色体功能组学研究,而且还可能用于查找特定疾病相关的染色体异常（如DNA突变、异位、重复及倒置等）,具有一定的实用意义。

英文摘要：

Target enrichment methods have high uniformity,specificity and sensitivity,which require relative low sequencing depth to generate adequate coverage for the subsequent analysis. They are widely used in the resequencing of the particular genomic regions and chromosome conformation study etc. To enrich chromosome-special fragments of the sequencing libraries, chromosome 21 was chosen to demonstrate the principle of work. We developed a method of chromosome-special target enrichment using the human embryo liver diploid cells CCC-HEL1 as material. The experimental procedure is as follows：firstly,suspensions of chromosomes were prepared and single chromosome was sorted by flow cytometry after cell cycles synchronization. Secondly,sorted single chromosome was amplified by multiple annealing and looping-based amplification cycles（ MALBAC） and the amplification products were used to construct the DNA library. Finally,the library was hybridized and captured using the in vitro transcription andbiotin-labeled RNA probes in liquid phase condition. The capture efficiency was evaluated/verified. The q PCR results showed that specific target fragments were enriched in hundreds folds,while the whole library could be enriched around 60 folds. These data indicated that this method was successfully developed. The method might be not only useful for enrich special chromosome fragments for functional genomics research,but also useful for detecting diseases associated chromosomal abnormalities（ such as variation,translocation,duplication,inversion etc.）,which has certain practical value.