This is a powerful biotechnological tool used for the detection of gene expression

1. Kuvempu University
Sahyadri Science College, Shivamogga.
PG Department of Biotechnology
Seminar on :
DNA Microarray: Illuminating the Genetic Landscape
Presented By:
SAMPATH KUMAR K M
2nd Msc 4th Semester
PG Dept of Biotechnology
Sahyadri science college
Shivamogga.
Under the guidance of:
Mr. Abdul Shafiulla
Lecturer
PG Dept of Biotechnology
Sahyadri science college
Shivamogga.

2. Contents:

3. What is DNA Microarray Technology?
It is a technique that immobilizes nucleic
acids to a surface (chip) and are used to
measure the relative concentration of
nucleic acid sequences in a mixture.
The bio-chips are of plastic, glass or
silicon.

4. DNA microchips are used to detect the
simultaneous expression of thousands of genes.
Each spot has a unique DNA Sequence or
gene.
The DNA molecules attached to each slide act
as probes to detect gene expression, followed
by the hybridization of fluorescently labelled
cDNA with these probes.
Up to 6500 genes can be detected in a single
bio-chip.

5. History:
Proposed in Late 1980s by Augenlicht and his
contemporaries.
The main idea of microarray was evolved from
Southern Blotting.
They radioactively labelled approximately 4000
cDNA sequences to analyze the gene expression of
colon tumors and its types at different stages of its
proliferation.

6. How it works:

7. Collection of samples:
Collection of target sample :
Collect biological samples (cells, tissues) of interest.
Isolate total RNA using RNA extraction kits or
protocols.
Preparation of probe :
the term "probe" typically refers to the short DNA
sequences that are immobilized on the microarray slide.
These probes are designed to be complementary to
specific target genes or sequences of interest.

8. mRNA to cDNA synthesis:
The process of converting messenger RNA
(mRNA) into complementary DNA (cDNA) is
known as reverse transcription.
This process is a crucial step in DNA microarray
analysis.

9. cDNA tagging:
After synthesizing cDNA from mRNA using
reverse transcription, you can introduce labels
or markers to the cDNA.
Common labels include fluorescent dyes
(e.g., Cy3, Cy5) or non-fluorescent molecules
(e.g., biotin).
This labelling step helps in visualizing and
detecting the cDNA during subsequent
experiments.

10. Hybridization:
Hybridization is the process of binding labeled
DNA (cDNA) from experimental and control
samples to complementary DNA probes
immobilized on a microarray slide.
Hybridization enables simultaneous analysis of
gene expression levels and helps identify
differences between samples.
The intensity of bound DNA indicates gene
expression

11. Scanning and data interpretation:
Scanning:
A microarray scanner is used to scan the
microarray slide. The scanner excites the
fluorescent dyes using specific wavelengths of
light.
The emitted fluorescence signals are detected and
converted into digital intensity values for each
spot (each probe) on the microarray.

12. Data Collection:
The scanner generates a digital image file
containing intensity data for each spot. The
intensity values represent the amount of labeled
cDNA bound to each probe.
Data Analysis:
The intensity data is analyzed using software to
quantify gene expression levels and compare
differences between experimental and control
samples.

15. TYPES OF DNA MICROARRAY:
1. Spotted DNA arrays (cDNA arrays):In Spotted DNA arrays, bio-chips are
made up by cDNA which are amplified by PCR. They are then immobilized on a
solid support. After which probe DNA is loaded into a spot by Capillary action.
2. Oligonucleotide arrays : In these microarrays, few mers long oligonucleotides
are spotted in the bio-chip. More than one probe is used in this array to express
each gene. It is more Flexible, rapid but an expensive technology.

16. Applications
Forensic
Science
Personalized
Medicine
Infectious
Diseases
Vaccine
Development
Pharmacogeno
mics
Disease
Research

17. Limitations :
While DNA microarrays offer powerful insights into gene expression and
genetic analysis, they also have certain limitations :
Cross-Hybridization
Probe Design Challenges
Technological Advancements
Not Suitable for Single-Cell Analysis

18. Conclusion
DNA microarrays have revolutionized gene expression analysis, aiding diverse
fields from disease research to personalized medicine. Despite limitations, they
remain crucial for understanding complex genetics. As technology progresses,
microarrays complement newer methods, maintaining their importance in molecular
insights.

19. Reference
https://chat.openai.com/?model=text-davinci-002-render-sha
Microarray Technology and Its Applications. (2014). Edited by: Ulf
Landegren. Springer. ISBN: 978-3-319-06027-7.
Chena, M., Shalon, D., Davis, R. W., & Brown, P. O. (1995).
Quantitative monitoring of gene expression patterns with a
complementary DNA microarray. Science, 270(5235), 467-470.