The Justice Department recognizes that DNA can indeed be used to invent things (pdf):
…the district court erroneously cast doubt on the patent eligibility of a broad range of man-made compositions of matter whose value derives from the information-encoding capacity of DNA. Such compositions — e.g., cDNAs, vectors, recombinant plasmids, and chimeric proteins, as well as countless industrial products, such as vaccines and genetically modified crops, created with the aid of such molecules — are in every meaningful sense the fruits of human ingenuity and thus qualify as “‘human-made inventions’” eligible for patent protection…
At the same time, the DOJ distinguishes between the above inventions and isolated genomic DNA, which does not qualify:
…genomic DNA that has merely been isolated from the human body, without further alteration or manipulation, is not patent-eligible. Unlike the genetically engineered microorganism in Chakrabarty, the unique chain of chemical base pairs that induces a human cell to express a BRCA protein is not a “human-made invention.” Nor is the fact that particular natural mutations in that unique chain increase a woman’s chance of contracting breast or ovarian cancer. Indeed, the relationship between a naturally occurring nucleotide sequence and the molecule it expresses in a human cell — that is, the relationship between genotype and phenotype — is simply a law of nature.