Transcript Section 6: Molecular Biology

Molecular Biology
It’s a Matter of Perspective
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.

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
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.
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.
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.
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.