Whole genome sequencing (WGS) determines nearly the entire DNA base sequence of an individual. In medicine, it can identify genetic variants associated with disease and help clinicians select diagnosis, prevention or treatment strategies suited to that person.
How the process works
- DNA is extracted from a patient’s cells and fragmented.
- Sequencing technology determines the order of bases in millions of fragments.
- Bioinformatics software assembles or aligns these sequences against a reference genome.
- Differences called genetic variants are identified. These include base substitutions, insertions and deletions.
- Clinicians assess whether relevant variants are associated with disease risk, drug response or treatment outcome.
| Medical use | How WGS contributes |
|---|---|
| Diagnosing genetic disorders | It may identify a disease-causing variant, especially when symptoms could result from many different genes. |
| Cancer analysis | Comparing DNA from tumour and non-tumour cells can reveal somatic mutations that may influence treatment. |
| Predicting disease risk | Some variants indicate increased susceptibility, although genes do not determine all diseases because environmental factors also affect phenotype. |
| Pharmacogenomics | Variants affecting drug metabolism can help predict whether a drug will be effective or cause adverse effects. |
| Personalized medicine | Genomic information can help tailor monitoring, prevention and treatment to an individual’s genotype. |
A common misconception is that WGS gives a definite prediction of a person’s medical future. Most variants have uncertain or very small effects, and many phenotypes result from interactions between multiple genes and environmental factors. Interpretation also requires comparison with reliable databases and raises issues involving privacy, consent and access to treatment.
Exam technique
This is assessable at both in A3.1, including the potential use of WGS in personalized medicine. For an question, link each stage clearly: sequencing identifies variants → variants may affect proteins or gene expression → this information can inform diagnosis or treatment. Avoid merely stating that WGS “finds diseases”; it identifies variants that must be interpreted.
