Animal Biotechnology and Modeling
211
Transgenic Founder
The frst-generation transgenic organism directly produced as a result oF gene
transFer/germ plasm manipulation procedures. The term does not imply that the
transFerred gene (transgene) is heritable to Future generations.
Transgenic Line
A direct Familial lineage oF organisms derived From one or more transgenic Founders,
characterized by the passing oF the transgene(s) to successive generations as a stable
genetic element. The line includes the Founder and any subsequent oFFspring inheriting
the specifc germ line manipulation.
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Transgenic animals and our ability to manipulate the genome oF whole animals
in vivo
have influenced the liFe sciences in dramatic Fashion. In less than 15 years, practical
aspects oF germ line manipulation oF the genetic composition oF animals have allowed
researchers to address Fundamental questions in felds ranging From medicine
and biology to biotechnology and production agriculture. Studies emanating From
basic eFForts in gene regulation have led the way to
in vivo
gene-transFer studies
Focused on the expression oF Foreign genes and the ablation oF endogenous genes.
Our appreciation oF basic biological development in animals and the potential
ramifcations oF novel phenotypes resulting From genetic engineering eFForts have
been markedly influenced by pioneering eFForts in transgenic animal technology.
1
Introduction
1.1
Brief History and DeFnition of Transgenic
Animals
The ability to introduce Functional genes
into animals provides a very powerFul tool
For dissecting complex biological processes
and systems. Hence, transgenic animals
represent unique models that are custom-
tailored
to
address
specifc
biological
questions. ±urthermore, classical genetic
monitoring
cannot
engineer
a
specifc
genetic trait in a directed Fashion. ±or
identifcation oF interesting new models,
the genetic screening and characterization
oF chance mutations remains a long and
arduous task. ThereFore, gene-transFer is
also oF great value, particularly For animal
species in which long liFe cycles reduce
the value oF classical breeding practices For
genetic modifcation.
Although the entire procedure For mi-
croinjection into living cells was described
in the late 1960s, it took 15 years be-
Fore transgenic animals were created. In
1980 and 1981, six pioneering laborato-
ries reported successFul gene transFer and
the production oF transgenic mice. Their
success would not have been possible,
however, were it not For the refnement oF
recombinant DNA technologies needed to
develop viable protocols and to document
results. In gene transFer, animals receiv-
ing new genes (Foreign DNA sequences
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