BGI sequencing platform

Sequencing Principle

DEBSEQTM is remarkable for its low amplification error rate and low repetition rate of output data, which is established on a novel sequencing strategy based on DNBs (DNA nanoballs).
Targeted DNA fragments is denatured to single strand DNA and generate single strand circular DNA (sscirDNA) by adding a splint oligonucleotide with a complementary sequence to 5' and 3' terminal ends.
DNBs are generated by hundreds of rounds of rolling circle amplification (RCA) using sscirDNA as template. In this process, all amplifications are processed with original DNA insert as template, which largely avoid accumulation of errors and GC bias. Therefore, sequencing on base of DNBs is much preferable for SNP and indel detection.
A patterned active binding sites and distance are designed on the surface of flow cell. The binding of DNBs to the spots are firstly driven by electrostatic force and stabled by Van der Waals force. The uniformed size of spots enables one-to-one binding of DNBs on the spots and the larger distance between them empowers a non-interference read-out of each single DNB and reduced index hopping. This optimized patterned array largely saturates the flow cell with DNBs, which greatly increased the efficiency of flow cells.
cPAS technology is employed in sequencing process, where fluorescent signals are released while synthesizing and captured by imaging. The fluorescent signals are converted into digital signals for base-calling.