Introduction
to Microarray
Molecular Biology research evolves through the
development of the technologies used for carrying them out.
It is not possible to research on a large number of genes
using traditional methods.
What is DNA Microarray?? Ans:-DNA Microarray is a kind of
“Molecular Biology research”. Microarray is
one such technology which enables the researchers to investigate and
address issues which were once thought to be non traceable. One can analyze the
expression of many genes in a single reaction quickly and in an efficient
manner.
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.
A typical microarray experiment involves the
hybridization of an mRNA molecule to the DNA template from which it is
originated. Many DNA samples are used to construct an array. 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.
How this is carried out?? What is meant by” microplates”
or standard “blotting membranes”. The details of Microarray Technique:-
An array is an orderly arrangement of samples where
matching of known and unknown DNA samples is done based on base pairing rules.
An array experiment makes use of common assay systems such as microplates or
standard blotting membranes. The sample spot sizes are typically less than 200
microns in diameter usually contain thousands of spots.
What do we mean by
DNA probes?? Ans:-
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). The spots can be DNA, cDNA, or oligonucleotides. These are
used to determine complementary binding of the unknown sequences thus allowing
parallel analysis for gene expression and gene discovery. An experiment with a
single DNA chip can provide information on thousands of genes simultaneously.
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.
Types of Microarrays
Depending upon the kind of immobilized sample used
construct arrays and the information fetched, the Microarray experiments can be
categorized in three ways:
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.
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.
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.
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.
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