ARRAY TECHNOLOGY:

Based on RNA & DNA hybridization reaction.

Simultaneously several of gene can be analyzed.

Advantages :

• miniaturization.

• Development of fluorescent labelled nucleotides, which is detected by laser screening.

• Decreased use of hazardous & cumbersome radioactive labelled DNA.

Chips located with synthetic

oligonucleotides.

Chips located with a DNA

fragment isolated directly from

respective genes.

Principle:

Involves hybridization between 2 DNA strands.

A high no. of complementary base pairs in a nucleotide sequence has a tighter non-covalent bonding between 2 strands.

After washing off of non-specific bonding sequences, only strongly paired strands will remain hybridized.

Fluorescently labelled target sequences that bind to a probe sequence generate a signal that depends on the strength of hybridization determined by the no. of paired bases, the hybridization conditions and washing after hybridization.

Microarrays use relative quantitation in which the intensity of a feature is compared to the intensity of the same feature under a different condition, identity of the feature is known by its position.

Alternative : serial analysis of gene expression.

TYPES:

DNA microarray.

RNA microarray.

Protein microarray.

Antibody microarray.

Tissue microarray

Applications of DNA microarrays

• Monitor gene expression

– Study regulatory networks

– Drug discovery - mechanism of action

– Diagnostics - tumor diagnosis

• Genomic DNA hybridizations

– Explore microbial diversity

– Whole genome comparisons - genome evolution

– Identify DNA binding sites

– Diagnostics - tumor diagnosis.

DNA microarrays can be used to measure changes in expression levels, to detect single nucleotide polymorphisms (SNPs) , to genotype or resequencemutant genomes (see uses and types section).

DNA microarrays can be used to detect DNA (as in comparative genomic hybridization), or detect RNA (most commonly as cDNA after reverse transcription) that may or may not be translated into proteins. The process of measuring gene expression via cDNA is called expression analysis or expression profiling

H. GERHARD VOGEL ; DRUG DISCOVERY & EVALUATION;

CO EDITORS, JURGEN SANDOW ; 2ND EDITION;

PAGE NO : 19.

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