Human Whole Genome Sequencing (WGS)

Human Whole Genome Sequencing (WGS) provides a comprehensive, unbiased readout of an individual's complete genetic material. By determining the exact order of the approximately 3 billion nucleotide base pairs—adenine (A), thymine (T), cytosine (C), and guanine (G)—across all 23 chromosome pairs, WGS delivers an exhaustive profile of the nuclear and mitochondrial genomes.

Unlike targeted approaches, WGS captures both the ~1–2% of protein-coding regions (exons) and the remaining ~98% of non-coding genome architecture, including promoters, enhancers, introns, and intergenic regions critical to gene regulation and structural integrity.

Technical Overview & Sequencing Methodology

Modern high-throughput sequencing utilizes short-read (e.g., sequencing-by-synthesis) or long-read technologies to systematically resolve genomic variation across complex regions.

1. Library Preparation & Fragmentation

Genomic DNA (gDNA) extracted from biological samples (such as peripheral blood, tissue, or saliva) is mechanically or enzymatically fragmented into standardized insert sizes. Platform-specific adapters are ligated to fragment ends to facilitate cluster generation and priming during sequencing.

2. High-Throughput Sequencing

Base calls are generated in parallel across millions of spatial clusters. Optical or chemical signals corresponding to fluorophore-labeled or native nucleoside triphosphates are recorded per cycle, generating high-density raw sequence reads with associated Quality (Phred) Scores.

3. Bioinformatic Alignment & Variant Calling

·         Alignment: Raw sequence reads (FASTQ format) are aligned to a standardized human reference genome assembly (e.g., GRCh38/hg38 or T2T-CHM13) using high-performance aligners such as BWA-MEM or DRAGEN.

·         Variant Identification: Aligned data (BAM/CRAM format) undergo duplicate marking, base quality score recalibration, and variant calling to generate Variant Call Format (VCF) files detailing:

o    Single Nucleotide Variants (SNVs) and small Insertions/Deletions (Indels).

o    Structural Variants (SVs): Translocations, inversions, and large chromosomal rearrangements.

o    Copy Number Variations (CNVs): Duplications and deletions across chromosomal segments.

Primary Applications in Research & Clinical Diagnostics

• Rare & Undiagnosed Mendelian Disorders: Resolves causative variants in deep intronic, promoter, or complex structural regions that escape detection by exome or gene panel assays.
• Precision Oncology: Characterizes somatic mutation burden, mutational signatures, structural variations, and neoantigen candidates across cancer genomes.
• Population & Evolutionary Genomics: Delineates population structure, evolutionary drift, allele frequency distributions, and polygenic risk scores across diverse cohorts.
• Functional Genomics: Serves as a baseline map for integrating multi-omics data, including RNA sequencing (transcriptomics), ATAC-seq (chromatin accessibility), and methylation profiling (epigenomics).

Technical Specifications & Data Deliverables

• Sequencing Depth Options:
• 30x Coverage: Standard depth for germline variant identification and population genetics.
• 60x~100x+ Coverage: Deep sequencing for somatically mutated tissue, low-purity tumor samples, or mosaicism detection.
• Primary Standard Deliverables:
• Raw read data (.fastq.gz) with Phred quality scores.
• Aligned sequence reads (.bam / .cram).
• Raw and annotated variant calls (.vcf / .g.vcf).