Biochemistry · Topic
DNA microarrays !
A microarray is a chip with thousands of DNA probes that measures the expression of many genes at once or looks for gains and losses of genetic material.
Updated 2026-11-01
Key facts
- Thousands to millions of known-sequence probes fixed on a slide; the fluorescently labelled sample hybridises and a scanner reads each spot.
- Expression microarray: compares mRNA (as cDNA) from two samples, e.g. tumour versus normal tissue.
- Chromosomal microarray (CMA or aCGH): detects copy-number variants (microdeletions and duplications) across the genome.
- SNP arrays: genotype hundreds of thousands of polymorphisms; they also show loss of heterozygosity and uniparental disomy.
- It misses balanced translocations and new point mutations (karyotype or sequencing are needed for those).
In detail
- In aCGH the patient's and a reference DNA are labelled with different colours; the fluorescence ratio at each probe shows gain or loss.
- CMA is the recommended first test in children with intellectual disability, autism or multiple malformations without a clear cause.
- Expression profiles classify tumours and estimate prognosis (expression signatures in breast cancer).
- RNA sequencing (RNA-seq) has been replacing expression arrays in research.
- Also called
- Microarrays, DNA chips, CMA
Clinical notes
- It detects microdeletion syndromes such as 22q11.2, Williams (7q11.23) or Prader-Willi/Angelman (15q11-q13, with methylation testing).
- SNP arrays underpin ancestry tests and genome-wide association studies (GWAS).
Related
- FISH (fluorescence in situ hybridization)
- DNA sequencing
- Southern, Northern and Western blots
- Polymerase chain reaction (PCR)
Test yourself
Think of the answer, then tap the question to see it.
Which change does a chromosomal microarray detect, and which does it miss?
It detects gains and losses (copy-number variants); it misses balanced translocations.
What is the first genetic test in a child with unexplained intellectual disability?
Chromosomal microarray (CMA), together with fragile X testing.
What does an expression microarray measure?
The relative amount of mRNA from thousands of genes at once, comparing two samples.
Educational information, not medical advice. For any symptom, see a health professional.
Sources: DNA Microarray Technology Fact Sheet (National Human Genome Research Institute (NHGRI), 2026); Microarray Technology (National Human Genome Research Institute (NHGRI), 2026); What are the different types of genetic tests?: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2026); Textbook of Biochemistry for Medical Students, 6th ed. (Jaypee Brothers Medical Publishers (Vasudevan DM, Sreekumari S, Vaidyanathan K), 2011).
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Representative model, for educational purposes only.