Biology

NIOS Biology Chapter 30 Terminal Exercises

The NIOS Class 12 Biology Biotechnology chapter introduces modern biological techniques. Students learn about genetic engineering, bioprocessing, cloning, and applications in medicine and agriculture. It highlights the advantages and ethical issues of biotechnology.

Solved terminal exercises provide structured answers for revision. This chapter connects biology with modern technology and prepares students for higher studies and careers. It is an important part of the NIOS Class 12 Biology syllabus and exam preparation.

NIOS Class 12 Biology Biotechnology

1. Define biotechnology.

Biotechnology is defined as the industrial application of living organisms and their biological processes, such as biochemistry, microbiology, and genetic engineering, in order to make the best use of the microorganisms for the benefit of mankind.

2. How are alcoholic beverages produced by fermentation? Mention the steps in the process.

Alcoholic beverages are manufactured by the fermentation of sugars by the yeast, Saccharomyces cerevisiae. It is called Brewer’s yeast. The source of carbohydrate fermented by yeast gives the beverage its specific flavour. For example:

Wine is obtained by the fermentation of grapes. Grapes are fermented by S. cerevisiae, and their soluble sugars (glucose and fructose) are converted into CO2 and ethyl alcohol.
Fermentation is carried out in large tanks called bioreactors.
Barley malt is fermented to yield beer.

3. How can you make cheese and curd on a large scale?

On a commercial scale, the making of yoghurt as well as cheese utilises Rennet tablets.
Rennin is the milk curdling enzyme obtained from the calf stomach. However, this method is not popular anymore.
Whether by bacteria or by “rennin”, when milk is ‘curdled’, milk protein casein separates from the liquid, which is called whey.
Lactobacillus converts lactose in the milk into lactic acid, which lowers the pH.
Lowered pH causes souring, which is essential for preservation.
A starter culture of Streptococcus cremoris and Leuconostoc is added to the milk when butter, yoghurt, or cheese is made.

4. What are antibiotics? Name five antibiotics and their sources.

Antibiotics are substances produced by microorganisms, such as bacteria or fungi, which inhibit the growth of other microorganisms.

Tetracyclin	Streptomyces sp
Chlorotetracycline	Streptomyces auriefaciens
Chloramphenicol	S. venezuelae
Cycloheximide	S. griseus
Streptomycin	S. griseus
Cephalosporin	Cephalosporium acremonium
Penicillin	Penicillium chrysogenum

5. How are different generations of vaccines produced?

When vaccines are made from attenuated disease-causing bacteria, they are termed “first-generation vaccines”.
The “second-generation vaccines” have been produced by genetic engineering or recombinant DNA technology. Second-generation vaccines for the Hepatitis B virus and the Herpes virus are already in use.
Vaccines synthesised from chemicals are called “third-generation vaccines”.

6. Describe the steps in the production of biogas and mention the precautions to be taken.

Biogas is produced by the microbial activity on cattle dung in a specially designed tank called a digester. A mixture of water and cattle dung is poured into this digester, where anaerobic decomposition takes place and biogas is generated. This gas contains 55 – 70 per cent methane, which is inflammable, and it is generally used as cooking gas and for the generation of electricity.

7. Enumerate in a sequence the steps in recombinant DNA technology.

Recombinant DNA technology adds the desired gene, which is a DNA segment carrying a particular sequence of nucleotides, to the DNA of another organism (usually a bacterium) with the help of a transferring agent or vector. The resultant modified DNA is called recombinant DNA or rDNA.

The steps in the production of rDNA are as follows:

The desired piece of DNA is cut from the cells (e.g., human cells) with the help of enzymes called restriction endonucleases or restriction enzymes. These enzymes are found in different bacteria. They recognise specific nucleotide sequences in a DNA molecule and cleave (cut) them.
The same restriction enzyme cuts the same specific nucleotide sequence in a plasmid. A plasmid is a ring-shaped DNA molecule present in a bacterium. It is not part of the chromosome of the bacterium. It is used as a vector for transferring the foreign DNA into the host cell.
The desired DNA fragments are then mixed with the cleaved plasmids. These plasmids pick up the foreign DNA pieces with the same base sequence to replace their lost parts. These become the recombinant plastids, and the DNA is rDNA or recombinant DNA
The recombinant plasmids are now introduced into or mixed with their bacteria, which pick up the recombinant plasmids.
The R-plasmids in the bacteria multiply along with the host bacteria. Soon, a clone of bacteria with rDNA is obtained. Such a bacterial clone containing copies of the desired gene can be preserved for future use. For example, as already mentioned, the human insulin gene can be inserted into a bacterial plasmid, and insulin obtained from the bacterial clone when needed.

8. Describe the uses of genetic engineering.

Genetic engineering or rDNA technology can be used for various purposes:

To manufacture important compounds like vaccines, hormones, vitamins, antibodies, etc. The production of these substances is achieved by inserting genes responsible for them into the bacteria and then getting clones of these bacteria to produce the desired substances.
To manufacture enzymes used for making cheese.
To break down pollutants through recombinant bacteria (bioremediation).
To clone particular genes with the help of rDNA technology and build up a gene bank or a gene library.
To use rDNA for gene therapy to cure genetic disorders.
To raise useful plants (transgenic plants) resistant to herbicides (chemicals used to kill weeds) or insect pests by inserting genes in the plants through rDNA technology.

9. How can a transgenic animal be obtained?

Transgenic animals are produced by inserting the gene for growth hormone from one animal through genetic engineering into another. Transgenic goats can produce a blood-clotting protein in their milk. This may be useful for children suffering from disorders such as haemophilia, in which blood does not clot.

10. Write a note on bioremediation.

Cleaning up the environment using living organisms is called bioremediation. Genetically engineered bacteria can clean up pollutants from the environment. The transformed bacteria metabolically break down toxic pollutants into harmless compounds.

Mercury-resistant bacteria process metallic mercury (which damages the nervous system) into a nontoxic compound.

11. Define the term gene therapy. Under what conditions does it become necessary to opt for such a therapy?

Gene Therapy may be defined as a technique in which a patient (sufferer) is given healthy genes to replace the defective ones inherited from the parents, or to enhance the action/reaction of the genes they already have. Gene therapy is necessary as a mode of treatment for several diseases and other diseases, such as AIDS, haemophilia, atherosclerosis, leukaemia, lung cancer, etc.

12. What is meant by human somatic gene therapy? How does it differ from the germ line gene therapy? Which of the two have been successful so far and why?

Somatic gene therapy refers to the genetic transformation targeted at body cells that can help correct a genetic defect that is confined to a specific organ or tissue.

The germ line gene therapy genetically modifies the cells of the germinal epithelium or gametes, or zygote, which will lead to the creation of individuals who can carry the remedial genes to the next generation.

13. Discuss in brief the different types of somatic gene therapy.

Somatic gene therapy can be grouped under the broad categories of:

(a) Ex vivo gene therapy

(b) In vivo gene therapy

Ex vivo (outside the body) gene therapy involves the use of cells (with a defective gene) taken from the patient. After the gene alteration, when the same cells are transfused (transferred back), there is no immunological response.
In vivo (within the body) gene therapy includes direct delivery of a therapeutic gene into the cells of a particular tissue of the patient.
Antisense Therapy is designed to prevent or lower the expression of a specific gene, thus limiting the amount of translation of protein from the overproducing gene.