The invention discloses a single-chain molecular identifier adapter and a single-chain
DNA database creating method and application thereof to
circulating tumor DNA detection. The single-chain molecular identifier adapter comprises a stem structure formed by 14 base
pairing, a sequencing primer sequence and a molecular identifier sequence formed by 8 random nucleotides, wherein a base 'U' is inserted between the sequencing primer sequence and a stem structure sequence, and a stem-loop structure can be formed by annealing denaturation of the single-chain
nucleotide sequence. By single-chain DNAdatabase creating, technical problems of low sensitivity, fragmentation, low concentration and short ctDNA fragments in
liquid biopsy in application of an existing detection technique are solved. Accurately distinguishing whether sequencing reads identical in
genome coordinate beginning and end loci come from cfDNA released by the same one or multiple germinal
cell is realized, sequencing reads derived from original positive and negative chains of the same
cell are paired for analysis, and accordingly sequencing rehandling is reduced, and the distinguishing rate of false positive
mutation isincreased.