The document discusses DNA microarrays or DNA chips. It explains that a DNA chip contains many copies of unique DNA sequences attached to a solid surface that are used to measure gene expression levels in cells. The presentation describes how DNA chips can compare gene expression levels between healthy and cancer cells to identify genes that are turned on or off in cancer. It provides examples of extracting RNA from tissue samples, converting it to cDNA, hybridizing it to a DNA chip, and analyzing the results to see differences in gene expression patterns between healthy and cancer cells. In conclusion, it states that DNA chips are a powerful comparative genomics tool for disease diagnosis, drug discovery, and toxicology research.

1. PRESENTATION ON:
AKANKSHA BISHT
B.TECH(BT)-5TH SEM
SUBMITTED BY:
BANASTHALI UNIVERSITY
SESSION:2016-17

2. • DNA chip or biochip
• Consists of a small glass
plate encased in plastic
• Collection of microscopic
DNA spots attached to a
solid surface
• Used to measure gene
expression level
• Each spot contains
multiple copies of a
unique DNA sequence
Image retrieved from www.learn.genetics.utah.edu

3. Image retrieved from www.learn.genetics.utah.edu
• Investigating human genes one or few at a time…
• Humans – around 20000 genes
In 20th century

4. Image retrieved from www.learn.genetics.utah.edu
Years passed…took a long time to investigate each gene

5. To learn about every gene in an organism in
ONE SINGLE EXPERIMENT!

6. • Evolved from southern blotting
• 1995-Miniaturized Microarrays first reported
• 1997- Microarray for a complete eukaryotic
genome

7. Image retrieved from www.learn.genetics.utah.edu

8. • Various types of cells in body are different from one
another due to different genes being “turned on” and
“turned off”. Image retrieved from www.learn.genetics.utah.edu

9. COMPARING DIFFERENCES IN GENE EXPRESSION
LEVELS IN HEALTHY CELLS AND CANCER CELLS
In cancer cells, Cell growth spin out of control
Image retrieved from www.learn.genetics.utah.edu

10. Healthy and Cancer tissue
sample taken
• Tissue samples dissolved in
organic solvent
• RNA extracted
• DNA, proteins and other cell
components separated
Image retrieved from www.learn.genetics.utah.edu

11. Mixing the tissue samples on
the Vortex RNA will be released
Samples are centrifuged to separate
RNA from rest of the cell
components
Image retrieved from www.learn.genetics.utah.edu

12. • After centrifugation, RNA separated from the rest
• Then both samples pipetted out in different collection tubes
Image retrieved from www.learn.genetics.utah.edu

13. • RNA Samples washed over
Columns filled with small
beads
• These beads bind only to RNA
strands with Poly-A tail
• Other molecules washed away

14. • Wash Buffer solution over beads
• mRNA detached from the beads
Images retrieved from www.learn.genetics.utah.edu

15. • DNA copy of the RNA is made giving it
some colour as labelling mix
• Green--Healthy cells RNA
• Red --Cancer cells RNA
Images retrieved from www.learn.genetics.utah.edu

16. • Reverse transcriptase
assembles labelled
nucleotides into a cDNA
molecule
• mRNA molecule degraded
Images retrieved from www.learn.genetics.utah.edu

17. Both the Samples are spread on the Microarray
Image retrieved from www.learn.genetics.utah.edu

18. • Microarray placed in washing solution
• Extra cDNAs that didn’t bind to the
slide are washed off
Image retrieved from www.learn.genetics.utah.edu

19. HEALTHY CELLS
• Many of the spots are Green but not every
• Dark Spots are genes not transcribed in Healthy cells
Image retrieved from www.learn.genetics.utah.edu

20. CANCER CELLS
• Red Spots pattern looks different
• Skin Cancer cells and Healthy skin cells have different
gene expression pattern
Image retrieved from www.learn.genetics.utah.edu

21. RED AND GREEN SPOTS
MERGED TOGETHER
• Yellow spot --gene
expressed both in healthy
cells and cancer cells
• Yellow genes—No change in
activity when cell becomes
cancerous
• Red spots--genes “turned-
on” in cancer cells
producing more mRNA
• Green spots --genes
“turned-off’ in cancer cells
Image retrieved from www.learn.genetics.utah.edu

22. • Gene Expression Profiling
• Comparative Genomics Tool
• Disease Diagnosis
• Drug Discovery
• Toxicological Research
Images retrieved from www.wikipedia.org

23. • Provides data for thousands of genes
• One experiment instead of many
• Huge step closer to discovering cures for
diseases
• Different parts of DNA can be used to study
gene expression

24. • DNA Chips are expensive to create
• Production of too many results at a time
requires long time for analysis
• DNA Chips do not have very long shelf life

25. • One of the most effective invention ever
developed
• Most powerful when used on species with
sequenced genome
• Readily accessible, widely used technology to
investigate biological systems
• Applications in wide array of biological
sciences

26. SOURCE:
• Kumar R, Sharma A, Tiwari R.K. Application of Microarray
in Breast Cancer:An Overview. J Pharm Bioallied Sci. 2012
Jan 4(1):21-6.
• Trevino V, falciani F, Hugo A.B. DNA Microarrays: A
Powerful Genomic Tool for biomedical and Clinical
Research. MolMed, 2007. Vol. 13(9-10)
NET SOURCE:
https://wikipedia.org
https://www.genome.gov
https://www.learn.genetics.utah.edu