Using DNA to detect and smother cancer
CATCHING FLAWED GENES: Research shows how DNA could be used to detect and control cancer
Scientists have created a miniature medical computer out of DNA that can detect cancer genes in a test tube and respond by releasing a drug.
Ehud Shapiro and his colleagues at the Weizman Institute of Science in Rehovot, Israel, developed a nanocomputer.
In this, strands of DNA serve as software that control the activity of enzymes. Trillions of these DNA- based computers could fit into a single drop of water.
The team targeted four genes that become either overactive or under-active in people with cancer. To detect changes in gene activity they designed a computer to have three components.
The first consists of short strands of DNA, called transition molecules that bind to a segment of the messenger RNA that each cancer gene produces. The scientists synthesized those segments and put various amounts of them in test tubes to simulate the presence or absence of cancer.
The second component is a computation module made up of a long DNA strand. It contains a series of nodes, each of which participates in a logic operation that determines a diagnosis from the RNA in the test tube.
Each operation relies on a series of reactions in which the transition molecules direct an enzyme to cut the module in one place or another.
This long DNA strand also harbours the computer's third component, a therapeutic fragment of DNA that binds to and suppresses the activity of a disease-causing gene.
In a positive diagnosis of malignancy, the computer's transition molecules detect changes in the activity of all four of a cancer's genesWhen the molecules determine that all four genes have abnormal activities, and the enzyme cuts the computation module so that it releases the drug. If the activity of only one of the four genes is normal, the diagnosis is `not cancerous'.
In these cases, the enzyme cuts off a different strand of the computer's DNA, which neutralizes the drug.
If the computer releases the drug by accident, a separate component keeps the system in check by simultaneously releasing the drug suppressor.
NAAGARAJU GOSU
M.Tech (Biotechnology)
ANU, Guntur
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