In terms of patentability, basically the position is very similar worldwide, with only a few variations in the details from country to country. Although these details are small, they may be vital in determining whether or not you can get a patent in a particular country.
To be patentable, an invention must pass the standard tests, that is be something man-made (i.e., invented not discovered), new, useful and not obvious to a person ‘skilled in the art’.
Naturally-occurring or engineered nucleic acid molecules are patentable subjects provided that they pass the aforesaid tests (i.e, naturally occurring molecules will be patentable so long as they were (re)-produced artificially). Strictly speaking the subject matter of a manufacture or composition patent claim is generally the DNA molecule itself, not the sequence listing. Although I believe that a patent directed to a DNA molecule may contain claims not only to the compound and composition, but also methods of use and processes for making the compound.
There are many sites out there that can let you know what a gene is. The common understanding of a gene differs a little from the original definition. A gene is a unit of hereditary information, although most people these days might say something like - genes are specific sequences of DNA that are central to the production of proteins.
As noted above, you can’t patent a ‘gene’. Instead, the claimable subject matter is usually DNA/RNA molecules, peptides, proteins, fragments etc. To obtain a patent you need to file a patent application with the relevant Patent Office and you will need to talk to your local friendly Patent Attorney who will give you all the information you need and guide you through the process. DO NOT disclose the information to anyone else before you talk to your Attorney or you may risk putting the information in the public domain which will kill your invention’s patentability.
These days you can no longer try a scatter-gun approach and just arbitrarily claim any DNA molecule you happen to isolate. You have to show that it has a specific purpose in order to be patentable, which means that you really have to have done a bit of research work with it before you can claim any rights to it. Also you cant just claim naturally occurring DNA unless you can actually produce it yourself artificially (i.e., in the lab).
In my jurisdiction (Japan) the answer is a firm…‘maybe’. Regardless of whether a particular expressed sequence tag already appears in a patent, that expressed sequence tag will only be patentable if you can show an “unexpected advantageous effect”. But good luck trying to show that, given that the ESTs are basically random base pairs whose only current commercial use seems to be as probes.
A good link for the U.S. position on some of these issues is the US Patent Office itself, which does an admirable job of providing such public information: http://www.patent.gov.uk/about/ippd/faq/biofaq.htm