Biomedical Engineering Reference
In-Depth Information
Gene manipulation and recombinant
DNA technology
3.1 Introduction
The biopharmaceutical sector is largely based upon the application of techniques of molecular
biology and genetic engineering for the manipulation and production of therapeutic macromol-
ecules. The majority of approved biopharmaceuticals (described from Chapter 8 onwards) are
proteins produced in engineered cell lines by recombinant means. Examples include the produc-
tion of insulin in recombinant
E. coli
and recombinant
S. cerevisiae
, as well as the production of
EPO in an engineered (Chinese hamster ovary) animal cell line.
Terms such as 'molecular biology', 'genetic engineering' and 'recombinant DNA (rDNA) technol-
ogy' are sometimes used interchangeably and often mean slightly different things to different people.
Molecular biology, in its broadest sense, describes the study of biology at a molecular level, but focuses
in particular upon the structure, function and interaction/relationship between DNA, RNA and pro-
teins. Genetic engineering, on the other hand, describes the process of manipulating genes (outside of
a cell's/organism's normal reproductive process). It generally involves the isolation, manipulation and
subsequent reintroduction of stretches of DNA into cells and is usually undertaken in order to confer
on the recipient cell the ability to produce a specifi c protein, such as a biopharmaceutical. 'rDNA tech-
nology' is a term used interchangeably with 'genetic engineering'. rDNA is a piece of DNA artifi cially
created
in vitro
which contains DNA (natural or synthetic) obtained from two or more sources.
When developing a new protein biopharmaceutical, one of the earliest actions undertaken entails
identifying and isolating the gene (or complementary DNA (cDNA); see later) coding for the target
protein, the generation of an appropriate piece of rDNA containing the protein's coding sequence
and the introduction of this rDNA into an appropriate host cell such that the target protein is made in
large quantities by that engineered cell. The drug development process and the cell types generally
chosen to produce recombinant proteins are described in Chapters 4 and 5 respectively. This chapter
aims to provide an introductory overview of the approaches and techniques used to isolate the target
gene, generate an rDNA sequence and introduce it into an appropriate producer cell. Before we look
at these techniques, however, we will briefl y review the basic biology and structure of nucleic acids.
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