NCERT Book Class 12 Biology Biotechnology Principles and Processes

BIOTECHNOLOGY : PRINCIPLES AND PROCESSES

Biotechnology deals with techniques of using live organisms or enzymes from organisms to produce products and processes useful to humans. In this sense, makingcurd, bread or wine, which are all microbe-mediated processes, could also be thought as a form of biotechnology. However, it is used in a restricted sense today, to refer to such of those processes which use genetically modified organisms to achieve the same on a larger scale.

Further, many other processes/techniques are also included under biotechnology. For example, in vitro fertilisation leading to a ‘test-tube’ baby, synthesising a gene and using it, developing a DNA vaccine or correctinga defective gene, are all part of biotechnology. The European Federation of Biotechnology (EFB) has given a definition of biotechnology that encompasses bothtraditional view and modern molecular biotechnology.The definition given by EFB is as follows: ‘The integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services’.

11.1 PRINCIPLES OF BIOTECHNOLOGY

Among many, the two core techniques that enabled birth of modern biotechnology are :

(i) Genetic engineering : Techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism.

(ii) Maintenance of sterile (microbial contamination-free) ambience in chemical engineering processes to enable growth of only the desired microbe/eukaryotic cell in large quantities for the manufacture of biotechnological products like antibiotics, vaccines, enzymes, etc.Let us now understand the conceptual development of the principles of genetic engineering. 

You probably appreciate the advantages of sexual reproduction over asexual reproduction. The former provides opportunities for variations and formulation of unique combinations of genetic setup, some of which may be beneficial to the organism as well as the population. Asexual reproduction preserves the genetic information, while sexual reproduction permits variation. Traditional hybridisation procedures used in plant and animal breeding, very often lead to inclusion and multiplication of undesirable genes along with the desired genes. The techniques of genetic engineering which include creation of recombinant DNA, use of gene cloning and gene transfer, overcome this limitation and allows us to isolate and introduce only one or a set of desirable genes without introducing undesirable genes into the target organism.

Do you know the likely fate of a piece of DNA, which is somehow transferred into an alien organism? Most likely, this piece of DNA would not be able to multiply itself in the progeny cells of the organism. But, when it gets integrated into the genome of the recipient, it may multiply and be inherited along with the host DNA. This is because the alien piece of DNA has become part of a chromosome, which has the ability to replicate. In a chromosome there is a specific DNA sequence called theorigin of replication, which is responsible for initiating replication.

Therefore, for the multiplication of any alien piece of DNA in an organism it needs to be a part of a chromosome(s) which has a specific sequence known as ‘origin of replication’. Thus, an alien DNA is linked with the origin of replication, so that, this alien piece of DNA can replicate and multiply itself in the host organism. This can also be called as cloning or making multiple identical copies of any template DNA. 

Let us now focus on the first instance of the construction of an artificial recombinant DNA molecule. The construction of the first recombinant DNA emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid (autonomously replicating circular extra-chromosomal DNA) of Salmonella typhimurium. Stanley Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance.

EXERCISES

1. Can you list 10 recombinant proteins which are used in medical practice? Find out where they are used as therapeutics (use the internet).

2. Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces. 

3. From what you have learnt, can you tell whether enzymes are bigger or DNA is bigger in molecular size? How did you know?

4. What would be the molar concentration of human DNA in a human cell? Consult your teacher.

5. Do eukaryotic cells have restriction endonucleases? Justify your answer.

6. Besides better aeration and mixing properties, what other advantages do stirred tank bioreactors have over shake flasks?

7. Collect 5 examples of palindromic DNA sequences by consulting your teacher. Better try to create a palindromic sequence by following base-pair rules.

8. Can you recall meiosis and indicate at what stage a recombinant DNA is made?

9. Can you think and answer how a reporter enzyme can be used to monitor transformation of host cells by foreign DNA in addition to a selectable marker?  product. The processes include separation and purification, which are collectively referred to as downstream processing. The product has to be formulated with suitable preservatives. Such formulation has to undergo thorough clinical trials as in case of drugs. Strict quality control testing for each product is also required. The downstream processing and quality control testing vary from product to product.

10. Describe briefly the followings:

 (a) Origin of replication

 (b) Bioreactors

 (c) Downstream processing

11. Explain briefly

 (a) PCR

 (b) Restriction enzymes and DNA

 (c) Chitinase

12. Discuss with your teacher and find out how to distinguish between

 (a) Plasmid DNA and Chromosomal DNA

 (b) RNA and DNA

 (c) Exonuclease and Endonuclease

Please refer to attached file for NCERT Class 12 Biology Biotechnology - Principles and Processes