DNA Microarray

Introduction

Understanding the structure of the human genome has allowed scientists to delve into the actual functions of specific genes, which is crucial for understanding health and disease. One powerful technique that enhances this understanding is the DNA microarray, which bridges the gap from genome structure to function. A microarray is a laboratory technique that enables the simultaneous examination of the expression of thousands of genes. These DNA microarrays are microscope slides printed with thousands of tiny spots in distinct positions, each containing a known DNA sequence or gene. These slides are often referred to as gene chips or DNA chips (Brown & Botstein, 1999; Schena et al., 1995).

DNA Microarray Technology

The DNA molecules attached to each slide act as probes to detect gene expression, commonly known as the transcriptome or the set of messenger RNA (mRNA) transcripts expressed by a group of genes. This high-throughput, highly parallel RNA expression assay technique allows for the quantitative analysis of RNAs transcribed from both known and unknown genes. The significance of this technique lies in its ability to provide diagnostic markers by comparing gene expression patterns in normal and pathological cells. Since it can simultaneously track the expression levels of many genes, it offers a source of operational context for predicting complex cell control systems (Lipshutz et al., 1999).

Methodology

To conduct a microarray analysis, mRNA molecules are typically collected from both a test sample and a control or reference sample. For instance, the reference sample could be from a healthy individual, while the test sample might be collected from an individual with a disease like cancer or a specific gene knockout. These mRNA samples are then converted into complementary DNA (cDNA), with each sample labeled with a fluorescent probe of a different color. For example, the test cDNA sample may be labeled with a red or pink fluorescent dye, whereas the control cDNA may be labeled with a blue fluorescent dye. The samples are then mixed and allowed to bind to the microarray slide. This binding process is known as hybridization (Lockhart et al., 1996).

Data Analysis and Interpretation

After hybridization, the microarray is scanned to measure the expression of each gene printed on the slide. If a particular gene's expression is higher in the test sample than in the control sample, the corresponding spot on the microarray appears pink or reddish. Conversely, if the expression in the test sample is lower than in the control sample, the spot appears blue. Finally, if there is equal expression in the two samples, the spot appears as a mix of both colors, resulting in a magenta color, given the colors mentioned above.

Conclusion

The data collected via microarrays can be used to create gene expression profiles, underscoring the importance of microarrays in illustrating instantaneous changes in the expression of numerous genes in response to a specific condition or treatment. This capability is invaluable for advancing our understanding of complex biological processes and for the development of targeted therapeutic interventions.

References

Brown, P. O., & Botstein, D. (1999). Exploring the new world of the genome with DNA microarrays. Nature Genetics, 21, 33-37.

Lipshutz, R. J., Fodor, S. P., Gingeras, T. R., & Lockhart, D. J. (1999). High density synthetic oligonucleotide arrays. Nature Genetics, 21, 20-24.

Lockhart, D. J., Dong, H., Byrne, M. C., Follettie, M. T., Gallo, M. V., Chee, M. S., ... & Brown, E. L. (1996). Expression monitoring by hybridization to high-density oligonucleotide arrays. Nature Biotechnology, 14(13), 1675-1680.

Schena, M., Shalon, D., Davis, R. W., & Brown, P. O. (1995). Quantitative monitoring of gene expression patterns with a complementary DNA microarray. Science, 270(5235), 467-470.