Liquid biopsies that analyze cell-free DNA in blood plasma are used for noninvasive prenatal testing, oncology, and monitoring of organ transplant recipients. DNA molecules are released into the plasma from various bodily tissues. Physical and molecular features of cell-free DNA fragments and their distribution over the genome bear information about their tissues of origin. Moreover, patterns of DNA methylation of these molecules reflect those of their tissue sources. The nucleosomal organization and nuclease content of the tissue of origin affect the fragmentation profile of plasma DNA molecules, such as fragment size and end motifs. Besides double-stranded linear fragments, other topological forms of cell-free DNA also exist—namely circular and single-stranded molecules. Enhanced by these features, liquid biopsies hold promise for the noninvasive detection of tissue-specific pathologies with a range of clinical applications.

用于分析血浆中无细胞DNA的液体活检用于非侵入性产前测试，肿瘤学和器官移植接受者的监测。DNA分子从各种身体组织释放到血浆中。无细胞DNA片段的物理和分子特征及其在基因组中的分布具有有关其起源组织的信息。此外，这些分子的DNA甲基化模式反映了其组织来源的模式。起源组织的核小体组织和核酸酶含量会影响血浆DNA分子的片段分布，例如片段大小和末端基序。除了双链线性片段外，还存在其他无细胞DNA拓扑结构形式，即环状和单链分子。通过这些功能进行了增强，