Whole Genome Sequencing (WGS)

Every living thing on Earth, whether human, animal, plant or even bacterium, has a "blueprint manual" that determines the traits and functioning of the body. This manual is written in a genetic code called DNA which consists of 4 chemical letters: A, C, G and T.

When we put together all the DNA in the cells of an organism, we call it its "Genome" For humans, our genome consists of more than 3 billion base pairs of these letters.

Therefore, Whole Genome Sequencing (WGS) is an advanced laboratory process used to "read" and arrange all 3 billion of these A, C, G, T letters from the first page to the last, in order to find abnormalities or understand our code of life in the greatest detail.

How is WGS done?

Genome sequencing has 4 main steps:

1 DNA Extraction

Extract DNA from sample cells, such as blood, saliva or tissue.

2 DNA Shearing

Because the genome is very large, machines cannot read it in one go, so sound waves or enzymes are used to cut the DNA strands into short pieces.

3 Sequencing

The DNA fragments are fed into a DNA sequencer, which reads the A, C, G, T letters in each fragment.

4 Assembly and Analysis

Computer systems and bioinformatics put the fragments that were read back together like a jigsaw puzzle, compare them with a "Reference Genome", and find mutations or abnormalities.

Benefits of Whole Genome Sequencing

WGS is transforming medicine, science and public health in many ways:

Precision Medicine: Helps doctors plan treatment suited to each individual's genetic code, such as targeted cancer treatment or assessing the risk of drug allergy (pharmacogenomics).
Diagnosing Rare Diseases: Many genetic diseases are hard to diagnose by usual methods. WGS helps find hidden mutations, so patients and families discover the cause of the disease faster.
Tracking Public Health Outbreaks: As we saw during the COVID-19 pandemic, scientists used WGS to sequence the virus to track mutations (such as the Delta or Omicron variants), leading to the development of more targeted vaccines.
Agriculture and Livestock: Used to develop plant and animal lines that resist disease or give better yields.

Challenges and Limitations

Despite its enormous benefits, WGS still faces challenges:

Huge Data (Big Data): One human genome produces a very large amount of digital data. Storing and processing it requires high-performance supercomputers.
Complex Interpretation: Even though we can read the whole code, we do not yet understand how every part of it works. Sometimes an abnormality is found but we cannot yet tell how it affects disease.
Ethical Issues: Genetic data is among the most sensitive personal data. Protecting privacy so that data is not used for discrimination (for example in insurance or employment) is a matter of global concern.

Conclusion

Whole Genome Sequencing is no longer just scientific technology confined to the lab, but is becoming an increasingly accessible tool (its price keeps falling compared with hundreds of millions of baht in the past). WGS is the key to unlocking the secrets of life, leading to personalized healthcare and improving the quality of life of humankind in the future.

References

Centers for Disease Control and Prevention (CDC). (n.d.). What is Genomic Sequencing? CDC - Genomic Epidemiology
National Human Genome Research Institute (NIH). (n.d.). Whole Genome Sequencing Fact Sheet. NIH - Whole Genome Sequencing
World Health Organization (WHO). (2021). Genomic sequencing of SARS-CoV-2: a guide to implementation for maximum impact on public health.
Nature Education. (2014). Whole-Genome Sequencing. Scitable by Nature