29-11-2012, 05:30 PM
BIOTECHNOLOGY : AN OVERVIEW
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EXECUTIVE SUMMARY
Biotechnology is defined as “any technical application that uses biological
systems, living organisms or derivatives thereof, to make or modify products
or processes for specific use”1. As such, biotechnology has existed since the
human race first used fermentation to make bread, cheese and wine.
Modern or “new” biotechnology refers to the understanding and application
of genetic information of animal and plant species. Genetic engineering
modifies the functioning of genes in the same species or moves genes across
species resulting in Genetically Modified Organisms (GMOs)
Starting with the discovery, in 1953, of the way genetic information is passed
from generation to generation2, modern biotechnology developed at an
accelerating pace in the second half of the 20th century. The recently
accomplished mapping of the human genome, i.e. the identification of the
about 30,000 genes that ultimately encode the hereditary characteristics of a
human being, has been described as a quantum leap in biology.
In the course of its short history, modern biotechnology has given rise to a
multitude of products and processes in the life sciences fields. In the health
sector human insulin was the first product to meet with commercial success.
Among processes, gene therapy still has to be proven but holds much
promise for treating genetic disorders and chronic diseases. Whilst cloning of
mammals is unlikely, given its complexity, to be viable from a breeding point
of view, it has a potential for the production of proteins with therapeutic value.
A Primer on the ‘Cell Factory’
Cell Organisation
All living matter – except viruses and prions4 – consists of cells. Some organisms are single
cells, e.g. bacteria, yeast, amoeba and some other parasites, while others consist of from
several (e.g. fungi) to several billions of cells. While, in principle, cells are similar in a number
of ways irrespective of their origin, in humans and other higher animals they are, in fact, also
highly specialised. Fig. 1 presents a diagrammatic, highly simplified cross section of a cell
containing a nucleus, m-RNA (ribonucleic acid), ribosomes, and endoplasmatic reticulum. All
this is enveloped by the cell membrane. The structures shown here are those directly
concerned with the cell’s production of proteins. Real cells contain several other structures,
the most important of which are the systems that provide energy for the intracellular
processes and those involved in maintaining an appropriate intracellular environment.
Transcription and Translation - from Instruction to Product
Transcription is the process in which a gene on the DNA molecule is used as a template to
generate a corresponding strand of messenger-RNA (mRNA), a molecule the structure of
which is related to that of DNA. The function of mRNA is to carry the coded messages from
the nuclear DNA to the ribosomes. Ribosomes may be ‘free’ in the cell plasma or attached to
the endoplasmatic reticulum (ER). Reading the sequence of base triplets, the ribosome
moves along the mRNA adding amino acids one by one, translating the original DNA code
into protein sequences. The ER is a 3-dimensional maze of connecting and branching
channels involved in the synthesis of proteins destined for secretion or storage, e.g. digestive
enzymes, hormones or antibodies, or the structural proteins for incorporation e.g. into cell
membranes. Proteins may also be modified in the ER by the addition of carbohydrate,
removal of a signal sequence or other modifications.
Monoclonal antibodies
While vaccines are antigens which, when inoculated, cause the immune system to produce
antibodies, recombinant technology is being used, as well, to produce antibodies directly. In
this variation on the immune/genetics theme, single cell lines, i.e. cloned, wholly identical,
specialised cells that can be grown indefinitely are used to produce antibodies of singular
specificity - monoclonal antibodies. These are used in a number of diagnostic applications, as
well as to prevent acute transplant rejection, and treat leukaemias and lymphomas. Some
show promise against auto-immune diseases.