Ever since man the hunter and gatherer gave up his nomadic way of life and began to tend stock and grow crops, he has been involved with genetic manipulation. Firstly, in ignorance, simply by choosing to rear particular animals or plants which were in some way advantageous to his developing lifestyle, and then much later, since the science of genetics began to develop, man has been engaged in breeding programmes designed to produce varieties of plants and animals exhibiting the specific characteristics which fit them to his various needs.
As man’s exploitation of natural resources has continued and industries have developed based on the synthetic ability of micro-organisms, particularly the bacteria and fungi, his need for knowledge of the fundamental principles of the genetics of these organisms has increased and the new science of molecular genetics has emerged. The discipline seeks to understand the molecular base of inheritance and the way in which the information encoded by deoxy-ribonucleic acid (DNA) is utilized by the living cell.
Advances in the field of recombinant DNA research over the past decade have given the geneticist the techniques required to mobilize individual genes, that is, specific sequences of DNA which code the amino acid structure of single proteins, and then transfer these genes from a donor to a recipient organism, thus conferring on the recipient the ability to synthesize the gene product. This is the practice of genetic manipulation as we understand the term today and which has become a cornerstone of the new Biotechnology.
Now, in addition to searching in nature for wild micro-organisms capable of producing specific products, a process which is often long and tedious and sometimes unrewarding, microbial hosts can be tailored for specific purposes by introducing foreign genes into them. The source of this foreign DNA can be microbial, animal, or plant and thus microbial hosts can be converted into biosynthetic factories capable of making a wide diversity of materials needed in every aspect of our lives from food and fuel to agriculture and medicine.
Most recombinant DNA experiments are designed to transfer specific genetic information from a donor organism to a recipient cell so that the newly acquired gene will be expressed and will result in the production of a ‘foreign’ protein. In order to do this, the DNA to be transferred must first be isolated from the donor organism and inserted into a DNA carrier or vector molecule which will be used to transfer it into its new host.
The ease with which fragments of DNA can be cut out of large DNA molecules, present in the chromosomes of plants and animals, and inserted into vectors, has been assisted greatly by the discovery within the last 20 years of a group of enzymes known as restricted endonucleuses. These enzymes recognize specific base sequences on DNA molecules and cut them precisely within or near that sequence. There are currently some three hundred of these enzymes known and some forty or so are commercially available in a highly-purified form.
The enormous growth of interest and input of capital into researching the applications of recombinant DNA research over the past decade is evidence of the potential benefit to man which these techniques can provide. Independent of its use for fundamental research in molecular genetics, a field which has provided and will continue to provide invaluable information to both academic and applied geneticists, recombinant DNA technology has already made important contributions in several areas of applied science.
A. The following list of points are not in order. Arrange them in the order in which they are mentioned.
a) how DNA transfer is carried out
b) specific examples of micro-organisms
c) the scope of molecular genetics d) man’s involvement in genetic manipulation
e) the sources of foreign DNA B. Mark the statements as True (T) or False (F). 1. Early man’s preference to grow particular plants is considered to be a kind of genetic manipulation. 2. The emergence of molecular genetics led to the onset of industries based on the synthetic ability of micro-organisms. 3. Genetic manipulation now is mainly the practice of transferring individual genes from one organism to another.
4. Only wild micro-organisms can act as hosts to foreign DNA.
5. Enzymes are used to identify and isolate DNA sequences. 6. There are about forty enzymes in the group known as restricted endonucleuses.
C. 1. What is a gene?
2. What happens when specific genetic information is transferred to a recipient cell