The law provides a patent for any person who invents or discovers any new and useful composition of matter. Of course, simply making an invention does not qualify for a patent. Specific formalities must be followed; papers must be signed and filed with the Patent and Trademark Office, fees must be paid. The invention is examined - a patentable invention must be novel, useful, and nonobvious.
Your genes while in your body do not qualify for a patent. But a gene from your body isolated in pure form in a test tube does qualify as a "composition of matter". The gene may be one never isolated before, or your own version of the gene may have a sequence unique to you. In either case your gene is novel.
This is similar to the patenting of antibiotic-producing bacteria. The bacteria which make streptomycin have been making streptomycin "forever" in nature in the soil. A pure culture of the bacteria freshly isolated from the soil is a "composition of matter" which never existed before and therefore could be patented.
A patentable invention also must be useful. You might argue that your insulin gene which merrily makes the hormone insulin in your pancreas is plenty useful. It keeps you alive. This personal sort of utility, however, doesnt impress the folks at the Patent Office. They seem be believe an invention should be useful to more than one person. Accordingly, patenting a human insulin gene required the isolation of the gene and its incorporation into bacteria, which then produced human insulin, a triumph of modern biology. The human insulin was isolated and proved superior to insulin isolated from animals for the treatment of human diabetes, in some cases.
The final requirement is that an invention be nonobvious to a skilled person. This requirement is asserted when the patent examiner discovers two or more publications which when combined, suggest the invention. In response your patent lawyer or agent amends the claims or asserts arguments that the invention actually was surprising and not obvious.
More than 20,000 patent applications for genes currently are pending. About 6000 gene patents have issued. Approximately 1000 of these patents are for human genes. Human gene patenting is here.
Perhaps you are opposed to commercial exploitation of your genes. Why not add some additional clauses to the many papers which seem to accompany medical procedures. Were always being asked to sign something, this would appear to be an opportunity to add something like - "for the medical benefit of the undersigned only." Or even better "for the medical or financial benefit of the undersigned only." Would this work? I dont know, but it might be fun to try.