Putting DNA to Work

Streamlining The Process

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Probing Many Viruses at Once

The “virus chip” is a DNA technology that was used successfully to identify the family of viruses to which SARS belongs in just 24 hours. Using a virus chip, SARS was compared to DNA samples from 1,000 viruses simultaneously.

The virus chip is an ordered arrangement of 11,000 specific 70-letter DNA sequences representing 1,000 different viral strains. They are the same DNA sequences that appear on the screen to the left. A sample of each 70-letter sequence is prepared and arranged as a tiny dot on a small glass slide. If samples from a sick person contain some of these same sequences, the dots containing the matching DNA sequences appear red, as in the enlarged photo above. Each dot in the photo, whether red or green, represents a different 70-letter DNA sequence.

From Dots to Bar Codes
Sorting the Dots for Easier Comparison

The virus chip software converts the red dots into lines on a bar code, such as this one. Since each virus has a unique combination of DNA sequences, each has a unique bar code.

Image of conversion of virus chip data to viral bar codes

The DNA matches that result in bar code lines are not always perfect. The brightness of each yellow line indicates how strong the match is. This is useful information because an unknown virus might be a new strain that is different from known strains. The SARS coronavirus, for example, was a new strain in humans.

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