A huge variety of naked/free nucleic acids are being produced in …

• Executive Summary
• ‘Naked’ and ‘free’ nucleic acids
• DNA persists in all environments and is readily taken up by cells of all organisms
• Hazards of naked nucleic acids
• The horizontal transfer of transgenic DNA
• The hazards of horizontal gene transfer
• Conclusion
• References
• Box 1: Naked nucleic acids in genetic engineering biotechnology
• Box 2 Free nucleic acids resulting from genetic engineering biotechnology
• Box 3: Hazards from naked nucleic acids
• Box 4: Reasons to expect that transgenic DNA may be more likely to spread horizontally than non-transgenic DNA
• Box 5: Potential hazards from horizontal gene transfer of naked/free nucleic acids
• Box 6: Possible links between genetic engineering biotechnology and the recent resurgence of infectious diseases
• Box 7: Current regulatory oversight is seriously out of date and does not address the dangers of naked or free nucleic acids

DNA - based

Viral genomes, eg, cauliflower mosaic virus, cytomegalovirus, vaccinia, baculovirus, adenovirus, SV40, many bacteriophages

cDNA of RNA viral genomes, eg, retroviruses SIV, HIV, Rous Sarcoma virus, mouse Moloney virus

Plasmids, eg, Ti of Agrobacterium, many plasmids from E. coli and yeast, often carrying antibiotic resistance genes

Transposons, eg, many broad host range transposons from E. coli with antibiotic resistance genes, some from Drosophila, such as mariner are found in all kingdoms

Artificial vectors made by recombining viral genomes, plasmids and transposons, carrying one or more antibiotic resistance genes; used for gene amplification, DNA sequencing, transfection, gene therapy, etc. [5], many are shuttle-vectors designed for replication in more than one species, ‘pantropic’ vectors cross many species barriers

Naked DNA vaccines, plasmid-based, viral vector based [6]

Artificial chromosomes: yeast (YAC) plasmid (PAC) and mammalian (MAC) made from telomeric and centromeric repeat sequences [7]

Artificial constructs: transgene cassettes, often include antibiotic resistance gene cassettes

PCR amplified sequences

Oligodeoxynucleotides (antisense), hairpin-forming oligodeoxynucleotides used in gene therapy [8]

RNA - based

Antisence RNA used in gene therapy

Ribozymes used in gene therapy [9]

Self-replicating RNA (linked to RNA-dependent RNA polymerase) used in gene therapy [10]

RNA vaccines

RNA-DNA hybrid

Chimeroplasty hairpins used in targeted gene mutation [11]