Method of the Month: Microarray Analysis
What makes one cell distinct from another? After all, we are made up of around 200 different cell types, so how do scientists differentiate between one or the other? The answer lies in the active genes in each cell. A gene is a segment of DNA that gets transcribed to RNA, and each type of cell has different genes activated within it to produce a distinct cell type. This accounts for the cell diversity in the human body.
Microarray analysis is one method scientists use to determine the active genes in a particular cell type. This type of analysis is primarily used in cancer research as it allows researchers to assess the active genes in a tumorous cell versus a healthy one. Classifying the genetic content of tumorous cells can aid in figuring out how to stop their growth or even eradicate them completely. Microarray analysis also works to identify genes with variants (a change in DNA sequence that is abnormal to the population). This is helpful because pathogenic variants (a variant fully or partially responsible for a disease) can be complex to locate among thousands of genes.
Microarray analysis begins with a microarray chip. A microarray chip is a small glass plate with several circular wells containing a specific known DNA gene sequence. When the chip is bathed with genes from the cell in question, they attach to their complementary sequence on the chip. This allows scientists to know what genes are active in a particular cell by observing which genes are matched on the microarray chip. Because DNA segments are too microscopic to see with the naked eye, fluorescent markers are attached before introducing the unknown DNA to the microarray chip. The fluorescent emission can be identified by passing a laser through the chip. The emission pattern is recorded by a computer which produces a colorful graph. The colors indicate which particular genes are present in the pathogenic cell, which are present in the normal cell, and which are present in both.
The question arises: How do researchers extract DNA segments from a cell? To start, they perform cell lysis (breakdown of a cell membrane) on a group of cells. The fragmented cells are then run through an extraction column, which can bind RNA and separate it from everything else. Lastly, the RNA is converted to DNA through a process called reverse transcriptase PCR. Reverse transcriptase PCR is a laboratory technique that allows for the conversion of RNA to DNA and the formation of multiple copies of that DNA. Now, researchers can work with the DNA alone and attach fluorescent markers to identify the patterns on the microarray chip.
Microarray analysis has been used in biomedical research, clinical diagnosis, pharmaceuticals, and cancer research. Although the procedure of microarray analysis can be complicated, its benefits to scientists in understanding our genes on a large scale are tremendous.
