The mantra of a patent professional is--novel, nonobvious, and useful! That is to say, in order to patent something, an inventor must demonstrate that her invention or discovery is new, substantially different from anything else that already exists, and has some sort of real use.
Up until now, defining "utility" has been difficult, particularly when DNA sequences are involved. But on 5 January, the United States Patent Office  (USPTO) issued final guidelines  on the utility requirement that will have direct consequences for scientists wishing to patent genes or other segments of DNA. Patents will not be issued for mere strings of As, Ts, Gs, and Cs. If you want exclusive rights to a particular DNA sequence, you now must define a "specific, substantial, and credible" use for it.
So, what does that mean exactly? Well, PTO examiners have actually been referring to interim guidelines that are very similar to the final rules since December 1999. For scientific examples and a clear explanation of the newly implemented terminology, download "The Revised Interim Utility Guidelines Training Materials" from the USPTO Web site (" Patent " section). Then, armed with this information, consult with your institution's tech transfer office or patent attorney and file those patents!