STEP 1
Represent each city by a single DNA strand containing 20 randomly chosen amino acid bases.
STEP 2
Represent the route between any two cities by a single DNA strand where the first 10 amino acid bases are the complementary bases to the last 10 bases in City 1 and the second 10 bases are the complementary bases to the first 10 bases in City 2.
STEP 3
Millions of stands of DNA representing every city and every possible route between any two cities are placed in a test tube where the strands combine. The end result is a slew of long strings of variable lengths formed by the strands combining.
To determine the solution, the researchers looked only for strings that have City 1 at one end and City 7 at the other. Among these strands, the researchers looked for only the strings that had seven cities. Among what was left, they looked for a string with seven different cities. That is the solution.
IMAGES BY JOHN MACNEILL
Back to Calculating with DNA