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Microarrays of DNA

PRESENTED BYABDULLAH AL MASUD(1202019)ATIQUR RAHMAN(1202053)

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2What is Microarrays of DNA?

An orderly arrangement of DNA sequences on a small solid support, usually a membrane or glass slide, used to quickly survey the simultaneous expression of many genes. Also called DNA chip or biochip.

Figure : DNA Chip

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3What is Microarrays of DNA?

Each spot on a microarray contains multiple identical strands of DNA. The DNA sequence on each spot is unique. Each spot represents one gene. Thousands of spots are arrayed in orderly rows and columns on a solid

surface (usually glass). The precise location and sequence of each spot is recorded in a computer

database. Microarrays can be the size of a microscope slide, or even smaller.

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4History

The concept of microarrays was first proposed in the late 1980s by Augenlicht and his colleagues.

Microarray technology evolved from Southern blotting.

They spotted 4000 cDNA sequences on nitrocellulose membrane and used radioactive labeling to analyze differences in gene expression patterns among different types of colon tumors in various stages of malignancy.

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5Requirements

DNA Chips

Target Sample (Fluorescently Labeled)

Enzymes

Fluorescent Dyes

Proves

Scanner

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6Process

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7Process

1.Sample Preparation

2.Purification

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8Process

3. Reverse Transcription

4. Labeling

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9Process

5.Hibridization

6. Scanning

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10Process

7.Normalization and analysis

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11Image Acquisition and Data Analysis

Gene is Not active in either normal or diseased sample

Gene is active in both normal and diseased sample

Gene is active in normal sample

Gene is active in disease sample

Figure: Small portion of DNA chip after Sacnning

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12Field of Microarrays of DNA

Gene Discovery Disease Diagnosis Drug Discovery Toxicological Research

and many more… …

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13Advantages

Provides data for thousands of genes.

One experiment instead of many.

Fast and easy to obtain results.

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14Limitations

The biggest disadvantage of DNA chips is that they are expensive to create.

Arrays provide an indirect measure of relative concentration

For complexity of designing arrays mammalian genomes DNA array can only detect sequences that the array was

designed to detect The DNA chips do not have very long shelf life.

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15Conclusion

Given the limitations of arrays mentioned above, it would be far preferable to have an unbiased method to directly measure all the DNA or RNA species present in a particular sample. The advent of next generation sequencing technologies combined with the rapid decrease in the cost of sequencing has now made sequencing cost competitive with microarrays for all assays with the possible exception of genotyping. It’s likely that DNA arrays will be fully replaced by sequencing methods within the next 5-10 years.

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16References

http://www.wormbook.org/chapters/www_germlinegenomics/germlinegenomicsfig1.jpg (10/12/15)

http://www.thefreedictionary.com/DNA+microarray (11/12/15) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4011503/ (13/12/15) http://www.premierbiosoft.com/tech_notes/microarray.html (13/12/15) https://

www.broadinstitute.org/mpr/publications/projects/genomics/Microarray_data_mining_facing%20_the_challenges.pdf (22/12/15)

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Thank You!

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The End

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