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‘Naked’ and ‘free’ nucleic acids
- Unregulated Hazards ‘Naked’ and ‘Free’ Nucleic Acids

‘Naked’ nucleic acids are DNA/RNA produced in the laboratory and intended for use in, or as the result of genetic engineering [1]. ‘Free’ nucleic acids refer to the laboratory-produced nucleic acids transfected into cells or organisms, whether incorporated as transgenic DNA or not, and subsequently released into the environment by secretion, excretion, waste disposal, death, industrial processing, or carried by liquid streams, or in airborne dust and pollen.

A huge variety of naked nucleic acids are being produced in the laboratory (see Box 1), which are used as research tools, in industrial productions, and in medical applications such as gene therapy and vaccines. They range from oligonucleotides consisting of less than 20 nucleotides to artificial constructs thousands of basepairs in length, and artificial chromosomes millions of basepairs long. The constructs typically contain antibiotic resistance marker genes plus a heterogeneous array of genes from pathogenic bacteria, viruses and other genetic parasites belonging to practically every kingdom of living organisms on earth [2]. Most of the naked nucleic acids and constructs have either never existed in nature, or if they have, not in such large amounts. They are, by definition, xenobiotics -- substances foreign to nature [3] -- with the potential to cause harm.

There is no regulation governing the release of naked nucleic acids into the environment. Many novel constructs are incorporated into transgenic micro-organisms and animal cell cultures for commercial drug production, and into crops, livestock, fish and other aquatic organisms for food, animal feed, and other purposes. These constructs are therefore greatly amplified, and at the same time introduced into foreign genomes where recombination with host genes and the genes of the host’s viral pathogens may readily occur. Transgenic wastes containing large amounts of free or potentially free transgenic DNA are being released unregulated into the environment, including those from microorganisms and cell cultures supposed to be in ‘contained use’ (see Box 2) [4]. Under the current EU Directive for Contained Use, contained users are allowed to release certain live transgenic microorganisms in liquid waste, and all killed microorganisms and cells containing transgenic DNA as solid waste.

The lack of regulation of naked/free nucleic acids is based largely on the assumption, now proven to be erroneous, that naked/free nucleic acids would be rapidly broken down in the environment and in the digestive system of animals [12]. Another assumption is that as DNA is present in all organisms, it is not a hazardous chemical, and hence there is no need to regulate it as such [13]. 

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