NGS 시퀀싱에서 대형 DNA 단편 선택 기술을 수행하는 방법

Large DNA fragment selection technology plays a critical role in NGS sequencing, particularly in structural variant detection, genome assembly, and haplotype analysis. Below are its core applications and technical principles:：

나. Application Scenarios

Structural Variant (SV) 발각

Challenge: Conventional short-read sequencing (예를 들어, Illumina) struggles to accurately capture variants >1 kb (insertions, deletions, inversions, translocations).

Solution: By selecting large DNA fragments (10–50 kb) for library construction, combined with long-read sequencing (PacBio/Nanopore) or linked-read analysis, complex SVs spanning repetitive regions can be resolved.

Example: Fusion events in cancer genomes (예를 들어, *ALK-EML4*) often require large-fragment data.

High-Quality Genome Assembly

Challenge: Short-read data often leads to assembly errors in repetitive regions, causing genome fragmentation.

Solution: Large fragments (예를 들어, Fosmid libraries) provide long-range physical linkage, enabling continuous scaffold assembly (5–10× improvement in N50).

Example: The T2T Consortium filled the final 8% gap in the human reference genome using Hi-C and ultra-long-read technologies.

Haplotype Phasing

Challenge: Short-read sequencing fails to preserve allelic linkage at heterozygous sites.

Solution: Barcode-based technologies (예를 들어, 10X Genomics) reconstruct haplotype blocks spanning hundreds of kb.

Value: Critical for HLA typing and identifying disease-causing gene linkages.

II. Core Selection Technologies

1. Physical Separation Methods

Pulse Field Gel Electrophoresis (PFGE): Separates fragments >50 kb for metagenomic or complex sample screening.

Magnetic Bead Selection (SPRIselect): Recovers specific fragment sizes (예를 들어, 0.1–10 kb or >15 kb) by adjusting bead-to-sample ratios.

2. Barcode-Based Enrichment

10X Genomics Chromium: Encapsulates DNA fragments in oil droplets, labeling short reads from the same large fragment with barcodes.

TELL-Seq/Linked-Reads: Uses microfluidics for virtual long-fragment reconstruction at 50% lower cost than 10X.

3. Circularization-Based Amplification

Loop Genomics: DNA fragments are circularized and amplified via rolling circle replication, preserving physical adjacency for standard NGS platforms.

III. Advantages vs. Conventional Methods

IV. Challenges and Optimization

High DNA Quality Required: Needs intact DNA (DV200 >50%), incompatible with FFPE samples to Development of low-damage extraction kits.

Cost Control: Long-read sequencing remains expensive to Hybrid strategies (예를 들어, Linked-Reads and Illumina) reduce costs.

Bioinformatics Upgrades: Specialized tools needed (예를 들어, Canu for assembly, HapCUT2 for phasing).

V. Representative Applications

COVID-19 Tracing: Nanopore sequencing and magnetic bead selection (>20 kb fragments) rapidly resolved SARS-CoV-2 genomes and recombination events.

Genetic Disease Diagnosis: 10X Genomics detected SMN1 exon 7 deletions, avoiding interference from SMN2.

Plant Genomics: In barley genome assembly, BAC libraries (40–100 kb) increased Contig N50 to 486 kb.

결론

Large DNA fragment selection overcomes the limitations of short-read NGS by providing long-range genomic context. With advances in barcoding (예를 들어, TELL-Seq) and localized platforms (예를 들어, MGI CoolMPS), this technology will accelerate applications in clinical diagnostics, evolutionary studies, and precision breeding.

공급자

상하이 링쥔 생명공학 유한회사, 주식회사에 설립되었습니다 2016 생체자성재료 및 핵산추출시약 전문제조업체입니다..

핵산 추출 및 정제 분야에서 풍부한 경험을 보유하고 있습니다., 단백질 정제, 세포 분리, 화학발광, 및 기타 기술 분야.

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