DNA microarrays are solid supports with organized grids of DNA probes that represent genes. Each DNA spot allows comparison of thousands of genes simultaneously. Microarray technology uses DNA chip probes to bind complementary DNA in samples, studying gene expression across entire genomes. Microarrays evolved from Southern blotting and were first used for eukaryotic gene expression profiling in 1995. Microarrays exploit DNA hybridization between nucleotide sequences to screen genomic sequences. They are used for gene expression profiling, drug discovery, diagnostics, and more.

1. Submitted By:
Rishabh Garg
M.Sc. Industrial
Microbiology
7895826925

2.  Definition: DNA microarrays are solid
supports, usually of glass or silicon, upon which
DNA is attached in an organized grid fashion. Each
spot of DNA, called a probe, represents a single
gene.
 There are several synonyms of DNA microarrays
such as DNA chips, gene chips, DNA arrays, gene
arrays and biochips.

3.  DNA Microarrays are one of the most
effective invention ever developed. A DNA
Microarray is a test that allows for the
comparison of thousands of genes at once.
Microarray technology uses chips with attached
DNA sequences as probes for gene expression.
Any DNA in the sample that is complementary
to a probe sequence will become bound to the
chip. Microarray technology is most powerful
when it used on species with a sequenced
genome. The microarray chip can hold
sequences from every gene in the entire
genome and the expression of every gene can
be studied simultaneously. Gene expression
data can provide information on the function of
previously uncharacterized genes.

4.  Microarray technology evolved from Southern
blotting, where fragmented DNA is attached to a
substrate and then probed with a known DNA
sequence.
 The use of miniaturized microarrays for gene
expression profiling was first reported in 1995, and
a complete eukaryotic genome (Saccharomyces
cerevisiae) on a microarray was published in 1997.

5.  The principle of DNA microarrays lies on the
hybridization between the nucleotide. Using
this technology the presence of one genomic or
cDNA sequence in 1,00,000 or more sequences
can be screened in a single hybridization.
 The property of complementary
nucleic acid sequences is to specifically pair
with each other by forming hydrogen bonds
between complementary nucleotide base pairs.

7.  There are 2 types of DNA Chips/Microarrays:
 cDNA Based Microarray
 Oligonucleotide Based Microarray

8.  cDNA Based Microarray- This type of chips are
prepared by using cDNA, it is called cDNA chips
or cDNA microarray or probe DNA. The cDNAs
are amplified by using PCR. Then these
immobilized on a solid support made up of nylon
filtre of glass slide (1 x 3 inches).
 Oligonucleotide Based- In oligonucleotide
microarrays, short DNA oligonucleotides are
spotted onto the array. The main feature of
oligonucleotide microarray is that each gene is
normally represented by more than one probe: the
ensemble of probes mapping to different regions of
the gene is usually called probe set. Commercial
oligonucleotide chips are available (e.g.
Affymetrix, Inc. GeneChip system)

9.  The DNA chips are used in many areas as given below:
 Gene expression profiling
 Discovery of drugs
 Diagnostics and genetic engineering
 Alternative splicing detection
 Proteomics
 Functional genomics
 DNA sequencing
 Toxicological research (Toxicogenomics)

10.  Provides data for thousands of genes.
 One experiment instead of many.
 Fast and easy to obtain results.
 Huge step closer to discovering cures for diseases
and cancer.

 Different parts of DNA can be used to study gene
expresion.

11. • The biggest disadvantage of DNA chips is that they
are expensive to create.
• The production of too many results at a time
requires long time for analysis, which is quite
complex in nature.
• The DNA chips do not have very long shelf life,
which proves to be another major disadvantage of
the technology.

12.  http://www.highveld.com/molecular-
biology/oligonucleotide-microarrays.html
 https://en.wikipedia.org/wiki/DNA_microar
ray
 Lehninger, 2005, DNA Chips, Principle of
Biochemistry, W.H. Freeman and Company,
Newyork, forth Edition, Pg. 326- 328
 Presscot M. Lansing, 2002, DNA Chips, Microbiology,
Athenaeum Press Ltd, Gateshead, Tyne and Wear,
Britain, Fifth Edition, 353 – 354.