Actually this is true.

If you find a cool rock on your property, and it does amazing things like cure slipped discs when put on your spine, you still can't patent it.

One can only patent inventions, things created and made or envisioned by man. You cannot patent a natural molecule, like calcium.

What the hell is the patent office doing issuing patents on naturally occurring genes?

The patentable subject matter criterion requires that the invention fall within the scope of inventions that Congress has designed the patent laws to protect. In § 101 of Title 35, Congress provides, "Whoever invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent therefor, subject to the conditions and requirements of this title." Because of this broad definition, the United States Supreme Court has focused on categories that do not fall within the patentable subject matter requirement. These categories include the following: 1) laws of nature; 2) natural phenomena; and 3) abstract ideas.

[link to topics.law.cornell.edu]

How did these companies get patents issued on naturally occurring genes?