<<More

Gene Sequencing

As an essential tool for modern life‑science research, gene‑sequencing technology has evolved from laboratory‑based research into clinical diagnostics and personalized medicine, greatly deepening our insight into life’s fundamentals and reshaping disease diagnosis and treatment strategies.

1. Basic Principles of Gene Sequencing Technology

The primary goal of gene‑sequencing technology is to identify the order of the four bases (A, T, C and G) within DNA molecules that store an organism’s complete genetic information. Ever since Frederick Sanger developed the chain‑termination method (first‑generation sequencing) in 1977, sequencing technology has delivered three transformative breakthroughs. Every advance brings exponentially higher sequencing throughput and sharply reduced costs.
1.1 Principle of First‑Generation Sequencing (Sanger Method)
Also known as the dideoxy chain‑termination technique, first‑generation sequencing employs 2',3'‑dideoxynucleotides (ddNTPs) to terminate chains amid DNA‑strand elongation.
1.2 Principle of Second‑Generation Sequencing (NGS)
The landmark innovation of next‑generation sequencing is the immobilization of DNA fragments onto solid substrates. Massively‑parallel reactions thereby enable ultra‑high‑throughput sequencing.
1.3 Principle of Third‑Generation Sequencing
Third‑generation sequencing centres on real‑time single‑molecule detection. It bypasses PCR‑amplification requirements and permits direct analysis of original DNA strands.

2. Key Performance Metrics of Sequencing Technologies

Advances in gene‑sequencing technology are chiefly driven by the Human Genome Project and large‑scale population genomics research. As sequencing has spread from major research hubs to routine laboratories and clinical facilities, new‑born disciplines including cancer genomics, microbiomics and single‑cell sequencing have emerged.
Core performance indicators for sequencing platforms are listed below:
2.1 Read Length
The quantity of continuous bases captured from one sequencing cycle. Longer reads simplify genome assembly and structural‑variant identification.
2.2 Accuracy
The success rate of base‑calling. Over 99.9%‑accuracy is generally mandatory for clinical deployment.
2.3 Throughput
Data output per run, which governs project scale and testing costs.
2.4 Sequencing Depth
The average coverage for each genomic segment, determining the sensitivity of variant discovery.
Priority over these indicators varies between application scenarios. Tumor‑mutation screening demands high accuracy and moderate coverage (30‑100X), whereas de‑novo genome assembly calls for long reads and high throughput.
As sequencing techniques mature, multi‑omics integration and real‑time data processing represent major emerging trends. Matching DNA‑sequencing datasets with transcriptomic (RNA‑seq), epigenomic (ChIP‑seq) and proteomic (mass‑spectrometry) data allows thorough investigation into genotype‑phenotype connections. Real‑time sequencing systems such as Oxford Nanopore permit on‑the‑fly data interpretation, delivering distinct strengths for fast pathogen diagnosis and field biological surveillance. Next‑generation fourth‑generation approaches including quantum‑based and electron‑microscopy sequencing are expected to overcome present‑day bottlenecks and deliver quicker, low‑cost genome decoding.

3. Workflow of DNA Sequencing

Despite differences in technical principles, modern sequencing experiments generally follow a similar standard workflow:
3.1 Sample Preparation:​ Extract high-quality DNA/RNA from samples such as blood or tissue, performing whole-genome amplification if necessary.
3.2 Library Construction:​ Fragment DNA (via ultrasonication or enzymatic digestion), perform end repair, and ligate sequencing adapters. This step may include size selection and PCR enrichment. Targeted sequencing also requires hybrid capture or amplicon PCR.
3.3 Cluster Generation/Template Preparation:​ Second-generation sequencing typically requires in vitro amplification to generate sufficient signal, such as bridge PCR (Illumina) or emulsion PCR (Ion Torrent). Third-generation sequencing can directly use native DNA molecules.
3.4 Sequencing Reaction:​ Run the corresponding chemical reactions based on the platform's characteristics, ranging from several hours (Ion Torrent) to several days (HiSeq X).
3.5 Data Analysis:​ Convert raw images or signals into base sequences (base calling), followed by quality filtering, alignment to a reference genome, variant detection, and other downstream analyses.

4. Application Fields of Gene Sequencing

By decoding DNA and RNA base sequences, gene‑sequencing technology has penetrated every branch of life science and medicine. Its far‑reaching applications spanning fundamental research, clinical practice, healthcare and crop breeding keep fueling breakthrough advances in relevant disciplines.
Typical application scenarios include:

5. Typical CNI Laser for Gene Sequencing

Most‑DNA‑sequencing techniques employ laser‑induced fluorescence, with four fluorophores marking A/C/G‑T and requiring dual‑ or four‑wavelength light‑source assemblies. CNI supplies abundant laser wavelengths (320‑690 nm, hundreds‑mW to several‑W) matched to fluorophore absorption peaks, alongside multi‑wavelength 365‑730 nm and white‑light LED sources; full specs are on www.cnilaser.com. Since sequencing runs take dozens of hours, our lasers satisfy strict long‑run demands: under‑1% 100‑hour RMS power stability, high spectral purity, OD＞5‑rejection and customizable beams with over‑90 % light‑field uniformity.