DNA structure: AT and GC bonds (IMAGE) University of Maryland Baltimore County Caption DNA is made up of adenine-thymine (AT) bonds and guanine-cytosine (GC) bonds. The frequency of each type of bond differs substantially across bacterial species. A new study uses this quirk of bacterial genetics to determine the origin and spread of various genes for antibiotic resistance. The new technique is so fast and inexpensive that it could be applied at regular intervals to track changes to bacterial genomes over time and detect emerging antibiotic resistance threats. Credit National Human Genome Research Institute Usage Restrictions No restrictions. License Public Domain Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.