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Mara wanted a straight answer to a strange report . In 1994 , Leonard Adleman had solved a small routing puzzle with DNA in a tube . He wrote , in the paper itself , that the graph was small enough to solve by looking . The interesting question was not whether DNA had beaten a computer . It was whether the molecules had really carried out the steps . He set a directed graph of seven vertices , with a chosen start and a chosen end , and asked for a path that visits each vertex once . He encoded each vertex , and each one - way link that really existed , as a short strand of DNA . Where a link was legal , those strands could bind , and an enzyme could join them into longer molecules . Huge numbers of strands met in the same tube , so many candidate paths formed together . The tube still did not hand him an answer . He had to keep only the molecules that began at the start and finished at the end , then keep only the length that meant exactly seven vertices , then check that every vertex was present . Those are ordinary steps on a molecular biology bench : copying , a gel , and a probe for each vertex . After that sorting , a molecule encoding a valid path was there to read . The experiment showed that DNA can try many possibilities at the same time . On a graph you can solve by eye , an electronic computer remains the practical tool . Adleman's point was the method . Synthetic biology takes a related ambition and turns it toward living cells . Older genetic engineering mostly moved a gene that already existed from one organism to another . This newer work tries to design genetic parts that behave in a planned way : a switch that turns a gene on only when two signals are both present . DNA synthesis lets a person order a sequence written on a screen . Tools such as CRISPR - Cas9 can cut an existing genome at a chosen place . None of that turns a cell into a reliable machine . A cell is wet , noisy , and full of its own chemistry , so a design that looks clean on paper can drift once it is inside . Mara closed the paper holding a smaller claim than the one she had come with , and a sharper one . In 1994 , DNA had been used as a material that computes . The work beside that experiment is not a promise that every illness or every factory will be rewritten . It is the practice of treating a genetic sequence as something a person can design , test , and correct , one careful construction at a time .
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