Microarray(cell biology)
- 2. Introduction • It is not possible to research on a large number of genes using traditional methods. • DNA Microarray is one such technology which enables the researchers to investigate and address issues which were once thought to be non traceable. • DNA Microarray technology has empowered the scientific community to understand the fundamental aspects underlining the growth and development of life as well as to explore the genetic causes of anomalies occurring in the functioning of the human body.
- 4. Technique 1. An array is an orderly arrangement of samples where matching of known and unknown DNA samples is done based on base pairing rules. 2. The sample spot sizes are typically less than 200 microns in diameter usually contain thousands of spots. 4. Thousands of spotted samples known as probes (with known identity) are immobilized on a solid support (a microscope glass slides or silicon chips or nylon membrane).
- 6. 5. An experiment with a single DNA chip can provide information on thousands of genes simultaneously. 6. An orderly arrangement of the probes on the support is important as the location of each spot on the array is used for the identification of a gene.
- 7. DNA Microarrays consist of 100 - 1 million DNA probes attached to a surface of 1 cm by 1 cm (chip). By hybridisation, they can detect DNA or RNA: If the hybridised DNA or RNA is labelled fluorescently it can be quantified by scanning of the chip.
- 8. DNA microarrays can be manufactured by: • Photolitography (Affymetrix, Febit, Nimblegen) • Inkjet (Agilent, Canon) • Robot spotting (many providers)
- 9. Affymetrix photolitography • Each probe 25 bp long • 22-40 probes per gene • Perfect Match (PM) as well as MisMatch (MM) probes
- 11. Robot Spotting
- 13. Types of Microarray 1. Microarray Expression Analysis: In this experimental setup, the cDNA derived from the mRNA of known genes is immobilized. The sample has genes from both the normal as well as the diseased tissues. Spots with more intensity are obtained for diseased 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.
- 14. 2. Microarray for Mutation Analysis: For this analysis, the researchers use gDNA. The genes 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 (SNP) and detecting them is known as SNP detection.
- 15. 3. Comparative Genomic Hybridization: It is used for the identification in the increase or decrease of the important chromosomal fragments harboring genes involved in a disease.
- 16. Applications of Microarrays • Gene Discovery: DNA Microarray technology helps in the identification of new genes, know about their functioning and expression levels under different conditions.
- 17. Applications of Microarrays • Disease Diagnosis: DNA Microarray technology helps researchers learn more about different diseases such as heart diseases, mental illness, infectious disease and especially the study of cancer.
- 18. Applications of Microarrays • Drug Discovery: Microarray technology has extensive application in Pharmacogenomics. Pharmacogenomic s is the study of correlations between therapeutic responses to drugs and the genetic profiles of the patients.
- 19. Applications of Microarrays • Toxicological Research: Microarray technology provides a robust platform for the research of the impact of toxins on the cells and their passing on to the progeny. Toxicogenomics establishes correlation between responses to toxicants and the changes in the genetic profiles of the cells exposed to such toxicants.