Microarray Technology
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[edit] Microarray Technology
' Microarray technology is qualitative or quantitative technique of measuring the gene expression.It is a collection of microscopic DNA spots, commonly representing single genes, arranged on a solid surface by covalent attachment to chemical matrix. DNA microrrays utilize the selective nature of DNA-DNA or DNA-RNA hybridization under high stringency conditions and fluorophore-based detection.DNA Microarray technology may be defined as a high throughput and versatile technology used for parallel gene expression analysis for thousands of genes of known and unknown function.However,in its precise and accurate definition of DNA microarray is an orderly arrangement of thousands of identified sequenced genes printed on an impermeable solid support, usually glass,silicon chips or nylon membrane.
[edit] Procedure involved
Step1: A DNA chip is taken which contains sequences of known gene that have been attached when manufacutured.
Step2: In the lab, tow samples are prepared, one being exposed to the putative toxicant. RNA is isolated and extracted. Reverse transcriptase is used to create cDNA which is single stranded.
Step3: The nucleotides used in the making the cDNA have been previously labelled so they be viewed on the chip.
Step4: The cDNA from the control and the treated population are mixed and applied to the chip. The cDNA hybridises to the single stranded DNA already on the chip.
Step5: Hybredisation produces a colour on the chip that is different from the colour of non-hybredised DNA.
Step6: Finally, genes that are active due to the toxicant can be differentiated from the genes that are inactive.
[edit] Types of Microarray
Depending upon the kind of immobilised sample used construct array and the information provides, the microarray experiments can be categorised in three ways:
1.Microarray expression analysis: In this experimental stepup, cDNA derived from the mRNA of known gene is immobilised. The sample has gene from both the normal as well as the diseased tissues. Spot with more intensity are obtained for disease tissue gene if the gene is over expressed in the diseased condition. This expression pattern is then compared to the expression pattern of a gene responsible for a disease.
2.Microarray for Mutation analysis: For this analysis, gDNA is used. The gene might differ from each other by as less as a single nucleotide base. A single base difference between two sequences is known as Single Nucleotide Polymorphism and detecting them is known as SNP detection.
3.Comparative Genome Hybredisation: It is used for the identification in the increase or decrease of the important chromosomal fragments harboring genes involved in a disease.
[edit] Application of Microarray
1.Disease Diagonsis: DNA microarray technology helps researchers learn more about different diseases such as heart disease, mental illness, infectious disease and especially the study of cancer. Until recently, different types of cancer have been classified on the basis of the organs in which the tumour develops. Now, with the evolution of microarray technology,it will be possible for the researchers to further classify the types of cancer on the pattern of gene activity in the tumour cells. This will tremendously help the pharmaceutical community to develop more effective drugs as the treatment strategies will be targeted directly to the specific type of cancer.
2.Drug Discovery: Drug Discovery is the hot cake of recent times and everyone want to have a bit of it. Well, Microarray technology has extensive application in pharmacogenomics. Pharmacogenomics is the study of correlations between therapeutic responses to drugs and the genetic profiles of the patients. Comparative analysis of the gene from the diseased and normal cells will help in the identification of the biochemical constitution of the protein synthesized by the disease genes. The scientific community can use this information to synthesize drug which combat with these protein and reduce their effects.
3.Toxicological research: Microarray technology provides a robust platform for the research of the impact of toxins on the cells and their passing on the progeny. Toxicogenomics establishes correlation between responses to toxicants and the change in the genetic profiles of the cells exposed to such toxicants.
