Genomic analysis using microarray

Sanjeet

A microarray is a tool for analyzing gene expression that consists of a small membrane or glass slide containing samples of many genes arranged in a regular pattern. 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 in the functioning of the human body.

Ø  A typical microarray experiment involves the hybridization of mRNA molecules to the DNA template from which it is originated.

Ø The amount of mRNA bound to each site on the array indicates the expression level of the various genes. This number may run in thousands. All the Data is collected and a profile is generated for gene expression in the cell.

Ø An array is an orderly arrangement of samples where matching of known and unknown DNA samples is done based on base pairing rules.

Ø The spotted samples known as probes are immobilized on a solid support. The spots can be DNA, cDNA or oligonucleotides. These are used to determine complementary binding of the unknown sequence thus allowing parallel analysis for gene expression and gene discovery.

Types of Microarrays

Depending upon the kind of immobilized sample used construct array and the information fetched, the microarray experiments can be categorized in three ways:

1.    Microarray Expression Analysis

2.    Microarray for Mutation analysis

3.    Comparative Genomics Hybridization

DNA microarray or DNA chips are fabricated by high-speed robotics, generally on glass but sometimes on nylon substrates, for which probes with known identity are used to determine complementary binding thus allowing massively parallel gene expression and gene discovery studies.

Major applications

1.    Identification of sequence.

2.    Determination of expression level of genes.

3.    Diseases diagnosis.

4.    Drug discovery.

5.    Toxicological research.

6.    In GEO (Gene Expression Omnibus).

Design of a DNA microarray experiment

1. Prepare DNA chip using target DNAs
2.  Generate a hybridization solution containing a mixture of fluorescently labelled cDNAs
3. Incubate hybridization mixture with DNA chip
4. Detect bound cDNA
5. Analyze data using computational method