Biology

NIOS Biology Genetics and Society Terminal Exercises

The NIOS Class 12 Biology Genetics and Society chapter explores how genetics influences human life and society. Topics include genetic engineering, cloning, ethical issues, and applications of biotechnology. Students learn about the benefits and risks of genetic advancements.

Solved terminal exercises provide exam-oriented answers. This chapter helps students understand the connection between science and society. It is a crucial part of NIOS Class 12 Biology and builds awareness along with exam preparation.

NIOS Class 12 Biology Genetics and Society

1. Name the three eras in the history of genetics.

The history of genetics can be traced to prehistoric times and can be classified into three eras as given below:

Early ideas: During this period, human activities included selecting, breeding, and domesticating plants and animals. Between 8000 and 1000 BC, horses, camels, oxen, and dogs had been domesticated. Between 7000 to 5000 BC, corn, rice, wheat, and date palm were being cultivated. Between the 17th and 19th centuries, unproven theories proposed the existence of epigenesis, preformationism, blending inheritance, and pangenesis.
Modern Genetics: Between 1902 and 1904, Gregor Johann Mendel proposed the chromosome theory of inheritance was accepted, and chromosomes, which could actually be seen under the microscope during cell division, were regarded as the ‘bearers of hereditary characters (genes)’. Mutations were recognised as a source of genetic variation. With the acceptance of Darwin’s theory of natural selection, geneticists studied the inheritance of traits in populations (Population genetics).
Molecular Genetics: By the mid-20th century, DNA was established as the genetic material. The helical structure of the DNA was proposed by Watson and Crick. The central dogma of molecular biology was established. Towards the end of this century, the other developments, such as a clear understanding of nucleic acid, proteins, genetics of bacteria, genetic engineering, gene cloning, organism cloning, DNA fingerprinting, genomics, bioinformatics, etc, were established.

2. Define gene cloning. What is the usefulness of a gene bank?

The production of large quantities of identical genes is called gene cloning. A gene bank, or a gene library or a DNA library, is, thus, a collection of bacterial or bacteriophage (virus) clones. Various clones of bacteria carrying the desired genes in their DNA can be stored and preserved at very low temperatures for their future use in a gene bank.

3. Give the various steps of recombinant DNA technology.

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.

4. What are the benefits 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.

5. What are transgenics? Give examples of a transgenic microbe, plant, and animal.

Genetically modified organisms are called transgenics.

Microbe: Bacteria
Plant: Bt Crops
Animal: Transgenic goats

6. Define genomics.

Genomics is the analysis of the genome data, that is, finding out the functional nucleotide sequences (genes) in the DNA of an organism.

7. Draw and explain a pedigree chart.

8. What is genetic counselling and why is it important?

Genetic counselling means advice given regarding a genetic disorder. Most defective genes

that cause genetic disorders are recessive. When both genes of a pair in the child are defective, the child is born with a genetic disorder. So if a couple wishes to know the chances of their child getting a particular disorder present in their family, they have to go to a genetic counsellor. The genetic counsellor has a very good knowledge of human genetics and can predict the chances of a genetic defect in a family.

9. What is DNA fingerprinting? Justify that it is the foolproof technique for sorting out paternity issues.

In 1984, Alec Jeffreys, a geneticist, invented a technique that could distinguish the DNA of a person from that of another, and he called this technique genetic fingerprinting or DNA fingerprinting.

DNA fingerprinting can be done from very small amounts of DNA, which are taken out of a tiny drop of blood, semen, hair follicle, tooth pulp, etc., picked up from the scene of a

crime. This is a foolproof technique as the

The lengths of these DNA pieces vary from person to person because of certain repeated sequences of nucleotides in DNA, which vary.
The DNA pieces are separated from each other according to size and charge with the help of a technique called electrophoresis.
The pattern that emerges is unique for each person.

10. List the steps of the Polymerase chain reaction.

In the technique called polymerase chain reaction (PCR), the DNA polymerase enzyme is used repeatedly to make many copies of a small fragment of DNA. Thus polymerase chain reaction

PCR helps in making many copies of a small amount of DNA.

The steps in PCR are,

The double helical DNA molecule is heated so that it breaks up into two strands.
Primers are added, and the DNA is cooled.
DNA polymerase is added, and in its presence, the two single strands acquire complementary strands, and so two molecules of the DNA are formed.

11. What are Bt crops? What are the benefits and fears related to their use?

Bt crops are genetically modified crops and are therefore also called transgenic crops. The name Bt crops is because the transgene or the foreign gene is transferred into the crop by the soil bacterium Bacillus thuringiensis (Bt).

Bt crops are incorporated with the ‘cry’ gene, which codes for the ‘cry protein’. Thus Bt crop produces this protein. When an insect pest eats the Bt crop, the cry protein is converted into a toxic substance by the enzyme present in the stomach of the pest. This toxic substance kills the pest.

The fears regarding Bt crops are,

Since Bt crops make the toxin throughout their growing season, pests may evolve that are Bt resistant.
Non-target species like the butterflies may die if they feed on Bt pollen.
Genetically modified crops may be harmful for the environment as they may pass the gene into a close relative plant, which may be useless for humans but will perpetuate as super weeds.

12. Write notes on (i) Biopatent, (ii) Biopiracy, and (iii) Necessity for a biosafety protocol.

(i) Biopatent:

Biopatent is the patent for for invention to be used as food, medicine/ drugs, alloys, semiconductors, etc. A patent may be granted for

(i) an invention or discovery
(ii) improvement of an earlier invention
(iii) process of generating a patent
(iv) a concept or design.

The duration of a patent is 20 years, and the patent holder has to obtain a license on certain reasonable terms and conditions. In India, the duration of a patent is 14 years, except for food and pharmaceuticals, which is only for 7 years.

(ii) Biopiracy

Biopiracy means patenting or exploiting a biological resource of another country without being authorised or giving adequate compensation. A rich developed country may patent a bioresource, such as a medicinal plant or traditional knowledge regarding a bioresource of a developing country. Sometimes, a useful biomolecule extracted from a plant growing in another country may be patented and used for commercial benefits. Even genes from foreign plants and animals may be patented.

(iii) Necessity for a biosafety protocol.

There is public concern about the possible hazards of using genetically modified (GM) organisms as food. The concern is about the safety of GM foods to humans and other animals, and also to the environment. Hence, in early 2000, several countries agreed to a Biosafety protocol by which the safety of using GM foods is first ascertained before using them. In our country, the Department of Biotechnology, in compliance with the rules of the Environment Protection Act (EPA), has to be consulted to grant permission for research and use of any GM organism only after testing its safety to humans, other animals, and the environment.