DNA sequencing technology is the basis of genetical genomics-related diseases. Sequencing by synthesis is one of the most important second-generation DNA sequencing techniques. Sequencing by synthesis can achieve a massively parallel sequencing effectively and improve sequencing throughput greatly, which favor cost reduction. Therefore, sequencing by synthesis has been widely used over the world. In DNA sequencing by synthesis, fluorescence-labeled nucleotides should be synthesized as a cyclic reversible terminator for DNA extension reaction. The reversible terminators reported in the literature mainly include MRT (mono-modified reversible terminators) and DRT (dual-modified reversible terminators) reversible terminators. The most significant advantage of DRT reversible terminator is that it can be readily identified by DNA polymerase. Besides, the synthetic route of MRT is simple, and this type of reversible terminator is hence more suitable for DNA sequencing by synthesis. Since fluorescence-labeled nucleotides are usually prepared by connecting the fluorescence tag and the nucleotide with a cleavable linker, the properties of the cleavable linker exert significant effects on the key parameters of DNA sequencing such as sequencing efficiency and read length. In this paper, recent advances and current research status of cleavable linkers used in DNA sequencing by synthesis is reviewed. Also, the development prospect of the cleavable linkers is demonstrated.

Contents
1 Introduction
2 Introduction of DNA sequencing technology
3 DNA sequencing by synthesis
3.1 Mono-modified cyclic reversible terminators
3.2 Dual-modified cyclic reversible terminators
4 Linkers
4.1 Enzymatic reversible terminators
4.2 Nucleophilic/alkali sensitive reversible terminators
4.3 Reduction-sensitive reversible terminators
4.4 Photosensitive reversible terminators
4.5 Metal-aided reversible terminators
4.6 Oxidation-sensitive reversible terminators
4.7 Electrophilic/acid-sensitive reversible terminators
5 Outlook