Microarray testing is a genetic analysis technique that can analyze thousands to millions of DNA sequences at once. By arranging a large number of DNA probes on a small chip and binding them to DNA or RNA in a sample, it is possible to examine the expression of specific genes and genetic variations. Microarray testing is used to analyze gene expression, detect genetic abnormalities, and discover disease-related genes.
How Microarray Testing Works
Array of DNA probes
Microarray chips contain a high density of DNA probes (short DNA sequences) corresponding to specific genes or sequences. Each probe corresponds to a specific gene or sequence and acts as an “antenna” to detect target molecules in the sample.
Sample Labeling
The DNA or RNA (e.g., mRNA) of the sample to be examined is labeled with a fluorescent dye, which increases detection sensitivity. For example, mRNA from cancer cells and normal cells can be labeled with different colored fluorescent dyes to compare the differences in gene expression between the two.
Hybridization
The labeled sample is applied to the microarray chip and waited for binding (hybridization) of the DNA or RNA in the sample to the probes on the chip. Binding to a specific probe indicates that the sequence is present in the sample.
Fluorescence signal measurement
After hybridization, the chip is scanned to measure the fluorescence signal. The intensity of fluorescence for each probe allows us to quantitatively determine the presence and expression level of each gene.
Microarray Testing Applications
Gene expression analysis
Microarrays are used to study differences in gene expression under different conditions. For example, by comparing the gene expression profiles of healthy and diseased cells, genes involved in disease can be identified.
Detection of Genetic Variants
It is used to detect chromosomal copy number abnormalities (e.g., duplications and deletions) and single nucleotide polymorphisms (SNPs). This allows for the diagnosis of inherited diseases and the detection of specific mutations in cancer.
Genetic polymorphism analysis
The distribution of SNPs and other genetic polymorphisms is analyzed to assess the impact of a particular genetic background on disease risk. It is also used in personalized medicine and drug response assessment.
Cancer Research and Diagnosis
Microarrays are used to identify genes that are abnormally expressed in cancer cells. This allows for the selection of treatment options based on the type and progression of the cancer, as well as the prediction of prognosis.
Advantages and Limitations of Microarray Testing
Advantages
A large number of genes can be analyzed at once, allowing efficient investigation of a wide range of gene expression and mutation.
Quantitative data can be obtained by fluorescence signals, and results can be obtained in a relatively short time.
Limitations
Since the sequences are predetermined, it is difficult to detect unknown sequences or novel mutations.
With the advent of next-generation sequencing (NGS) technology, more comprehensive genetic analysis is becoming possible, limiting the scope of use of microarray testing.
Conclusion
Microarray testing is a technique for rapidly and efficiently examining the expression levels and mutations of specific genes and sequences. It has a wide range of applications including gene expression analysis, identification of disease-related genes, and diagnosis of genetic abnormalities, and is still used in many research and clinical fields.
