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Unformatted text preview: DNA city names. The ligase in the mixture will then permanently concatenate the chains of DNA ﬂight numbers. Hence, the test tube contains molecules that encode random paths through the different cities (as required in the ﬁrst step of the algorithm). Because I began with such a large number of DNA molecules and the T For the map on page 56, there is only one Hamiltonian path, and it goes through Atlanta, Boston, Chicago and Detroit, in that order. Thus, the molecule encoding the solution will have the sequence GCAGTCGGACTGGGCTATGTCCGA. Unfortunately, although I held the solution in my hand, I also held about 100 trillion molecules that encoded paths that were not Hamiltonian. These had to be eliminated. To weed out molecules that did not both begin with the start city and terminate with the end city, I relied on the polymerase chain reaction (PCR). This important technique requires many copies of two short pieces of DNA as primers to signal the DNA polymerase to start its Watson-Crick replication. The primers used were the last name of the start city (GCAG for
Scientific American August 1998 59 Computing with DNA G C Copyright 1998 Scientific American, Inc. TOMO NARASHIMA G IRON BALL A G C C
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This note was uploaded on 11/28/2011 for the course COMP 790 taught by Professor Staff during the Fall '08 term at UNC.
- Fall '08