On September 2, 2003, the Biotechnology Industry Organization (BIO) issued what it called a "cloning factsheet," this being a document expressing objections to the Weldon Amendment, a measure under consideration in Congress that would prohibit the U.S. Patent Office from issuing patents on human embryos.  The entire factsheet is posted here.

What follows is footnote no. 1 in the factsheet:

   Four categories of inventions can be claimed: "a new and useful process, machine, manufacture or composition of matter." Any new and useful improvement to any of those may also be patented. The courts and the PTO [Patent and Trademark Office] have determined that multicellular living organisms, including animals, are patentable. In general, however, courts have interpreted the patent statute to deny protection for claims directed to "products of nature." Only things that have been specifically altered in their physical makeup through human intervention, and as a result differ from the corresponding products in their natural states, may be the subject of a U.S. patent claim. For example, a bacterium discovered in the wild may not be patented as a "thing," but a purified composition containing the bacterium in a form distinct from how it is found in nature may be patented. Similarly, an animal or human produced by conventional reproduction -- with no intervention by an "inventor" -- would not qualify as a patentable "manufacture" because it is a product of nature. Living organisms that possess physical characteristics resulting from human intervention qualify for protection because such living organisms are no longer "products of nature."