A microarray is a lab tool that detects the expression of thousands of genes at once using a hybridization technique on a solid substrate like a glass slide. It tells the sequence of target samples or any gene variations by hybridizing a large set of probes to the targets. DNA and protein microarrays are two common types. A DNA microarray has DNA probes attached to a solid surface that fluorescently labeled sample and target DNAs hybridize to, allowing analysis of gene expression. A protein microarray similarly has probes to track protein activities, functions, and interactions on a large scale through fluorescent hybridization and laser scanning.

2. Microarray
 A microarray is a laboratory tool used to detect the
expression of thousands of genes at once. It is a lab on
chip method. It is a hybridization technique usually
performed on two dimensional solid substrates, such as
glass slides or silicon thin-film cells. These slides are often
called gene chips.
 The target samples are hybridized with a large set of
oligonucleotide probes, attached to the solid support. It
tells us the sequence of the samples or any gene variation
in the sequence or used for gene mapping.

3.  It was first illustrated by Tse Wen Chang in 1983 for
antibody microarray.
 DNA and Protein Microarray are two of the many
types of microarray technology.

4. DNA Microarray
 A DNA microarray is more commonly known as a DNA
chip or biochip. DNA spots in picomoles (10-12) are
attached to a solid surface, that is known as probes. Both
the sample DNA and target DNA are either attached to
fluorophore or chemiluminescence labelled and then
allowed to hybridize.

5.  For example, mRNA from a healthy and diseased
individual is collected for the detection of disease. Both
the mRNAs are converted to cDNA and labelled with
green and red fluorescent dyes, respectively. The two
samples are then allowed to hybridize together.
 If the expression of healthy mRNA is more, a green dot is
seen on the slide. Similarly, a red dot is seen for higher
expression of the diseased mRNA. Finally, a yellow dot
appears on the slide when both the mRNAs are expressed
equally.
 The DNA chip can be studied this way for gene profiling,
SNP detection, comparative genomic hybridization, etc.

6. Protein Microarray
 Protein microarray, more commonly known as protein
chip, is a high throughput technique used to track the
activities, functions and interactions of proteins.
 The main advantage lies in the fact that a large number
of proteins can be tracked at once.

7.  Similar to DNA chips the probe proteins are fluorescently
labelled and allowed to hybridize with the target proteins,
the light emitted is read by a laser scanner.
 The solid surface used in protein microarray is glass slides,
nitrocellulose membrane, bead or microtitre plates.
 The technique is automated, rapid, sensitive, economical,
and requires small quantities of proteins and probes.

8. DNA vs Protein Microarray
DNA Microarray Protein Microarray
Definition
DNA microarray is an arrangement of DNA
spots (in picomole) attached to a solid
surface.
A protein microarray is a collection of
purified proteins on a solid surface.
Labelling
Either probe or target DNA is labelled or
both are labelled.
Only probes are labelled.
Solid surfaces
Glass slide or silicon thin-film cells. Glass slide, nitrocellulose membrane, bead
and microtitre plates.
Application
Used in gene expression profiling,
chromatin immunoprecipitation, SNP
detection, comparative genomic
hybridization, etc.
It is used in proteomics, diagnostics,
protein functional analysis, treatment
development and antibody
characterization.