1. Molecular Biology

2. It’s a Matter of Perspective The investigators who submit IBC protocols want to perform their experiments safely. The investigators who submit IBC protocols want to perform their experiments safely. However, their perception of the risks involved will not necessarily be the same as that of a biosafety professional. However, their perception of the risks involved will not necessarily be the same as that of a biosafety professional.

3. Risk Assessment The following risk assessment will identify the biological containment system to be used:  Properties of the donor organism  Nature of the DNA sequences that will be transferred  Properties of the recipient organism  Properties of the environment

4. Biological Expression System Most routine genetic engineering experiments can be performed safely in E. coli K12/pUC18 at BSL 1 provided the inserted foreign DNA sequences do not require a higher BSL.

5. Donor Organism and Cloned DNA Insertion of well-characterized DNA sequences that are unlikely to be involved in pathogenicity may not require additional safety measures. In cases where these sequences are not characterized, a situation that is typically encountered when a library of genomic DNA of an organism is being established, a higher BSL will be required. Cloning of genes coding for proteins that have potential pharmacological activity such as toxins may therefore require higher BSL.

6. Viral Vectors for Gene Transfer Although viral vectors used in gene therapy or gene transfer are replication-defective, they should be handled at the same BSL as the parent viral vector from which they are derived since the virus stocks may be contaminated with replication-competent viruses, which are generated by rare spontaneous recombination events in the complementing cell line.

7. Transgenic and “Knock-Out” Animals Animals carrying foreign genetic information (transgenic animals) should be handled in the containment level appropriate to the characteristics of the products of the foreign genes. For each new line of transgenic animal, the routes by which the animals can be infected, the inoculum size required for infection, and the extent of the virus shedding by the infected animal must be determined. Animals with targeted deletions of specific genes (“knock-out” animals) do not generally present particular biological hazards.