214
Animal Biotechnology and Modeling
pathways. With this caveat, considerations
include the ramifcations oF gene activity
From
intracellular
to
inter-
and
extra-
cellular events within a given tissue or
cell-type milieu.
Normally, gene Function is influenced by
cis-acting elements and trans-acting Fac-
tors. ±or transFerred genes, the cis- and
trans-activators, in conjunction with the
gene integration/insertion event within
the host genome, influence regulation oF
both endogenous and transFerred genes.
Using genes that code For reporter proteins
(e.g. oncogene or
lacZ
/
β
gal constructs),
analysis oF transgenic animals has re-
vealed the importance oF these Factors
in determining developmental timing, tis-
sue distribution, and relative eFfciency oF
gene expression. Transgenic animals have
also proven quite useFul in determining
in vivo
artiFacts oF other model systems
or techniques.
There are a number oF strategies in the
development oF transgenic mouse mod-
els, including systems designed to study
dominant gene expression, homologous
recombination/gene targeting and the use
oF ES cells, eFfciency oF transFormation oF
eggs or cells, disruption oF gene expres-
sion by antisense transgene constructs,
gene ablation or knockout models, reporter
genes, and marking genes For identifca-
tion oF developmental lineages.
1.3
Societal and Ethical Considerations
While gene-transFer technology continues
to open exciting new biological Frontiers,
it also raises questions concerning reg-
ulation and commercialization. It is not
within
the
scope
oF
this
presentation
to Fully address these issues; yet they
do exist and will continue to influence
the genetically engineered systems under
development.
Contrary
to
the
early
prospects
re-
lated to potential commercialization oF
this technology, there are societal chal-
lenges regarding perceived risks still ahead
(Table 2). The risks at hand can be de-
fned not only by scientifc evidence but
also in relation to public concern. There-
Fore, the central questions will revolve
around the proper saFeguards to employ
and the development oF coherent and
unifed regulatory guidelines. Can new an-
imal reservoirs oF Fatal human diseases
be created? Can more virulent pathogens
be artifcially created? What is the en-
vironmental impact oF the ‘‘release’’ oF
genetically engineered animals? Do the
advantages oF a bioengineered product out-
weigh potential consequences oF its use?
These are but a Few oF the questions that
we cannot ignore. Yet, the regulatory hur-
dles that exist today will challenge not
only scientists and policy makers, but aca-
demicians, bioethicists, and legal scholars
as well.
The strategies associated with the pro-
duction oF transgenic animals are quite
variable, even between laboratories that
utilize similar systems. However, most
oF the techniques For extensions to diF-
Ferent systems
are
unique
and
timely
Tab. 2
Societal concerns regarding genetically
engineered animals.
Environmental impact following ‘‘release’’ or
commercialization of transgenic animals
Public perceptions of perceived risk
Ethical considerations of transgenic animal
exploitation
Legislative oversight of technology
Safety of transgenic products, by-products, and
foodstuffs
Patent aspects and product
uniformity/economics of production
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