Exam Question for Class 12 Biology Chapter 12 Biotechnology and its Application
Please refer to below Exam Question for Class 12 Biology Chapter 12 Biotechnology and its Application. These questions and answers have been prepared by expert Class 12 Biology teachers based on the latest NCERT Book for Class 12 Biology and examination guidelines issued by CBSE, NCERT, and KVS. We have provided Class 12 Biology exam questions for all chapters in your textbooks. You will be able to easily learn problems and solutions which are expected to come in the upcoming class tests and exams for standard 12th.
Chapter 12 Biotechnology and its Application Class 12 Biology Exam Question
All questions and answers provided below for Exam Question Class 12 Biology Chapter 12 Biotechnology and its Application are very important and should be revised daily.
Exam Question Class 12 Biology Chapter 11 Biotechnology and its Application
Case Based MCQs
Case I : Read the following passage and answer the questions from 41 to 45 given below.
Insulin used to cure diabetes was earlier extracted from pancreas of slaughtered cattle and pigs. Insulin extracted from an animal source, though caused some patients to develop
allergy or other types of reactions to the foreign protein. Human insulin consists of two short polypeptide chains : chain A and chain B, that are linked together by disulphide bridges.
In mammals including humans, insulin is synthesised as a pro-hormone which contains an extra stretch called the C-peptide. This C peptide is not present in mature insulin and is
removed during maturation into insulin.
Question. The following is a list of some stages involved in producing human insulin from genetically engineered bacteria.
1. The bacteria are cultured in a fermenter for large scale production.
2. Recombinant insulin is extracted from the bacterial cells that expresses insulin gene.
3. The same restriction enzyme is used again to cut the bacterial plasmid for insertion ofthe human insulin gene.
4. Bacteria take up the plasmid carrying the insulin gene.
5. A restriction enzyme is used to cut human DNA to extract the insulin gene.
Select the correct order of these stages.
(a) 1, 5, 3, 4, 2
(b) 2, 4, 3, 5, 1
(c) 4, 5, 3, 2, 1
(d) 5, 3, 4, 1, 2
Answer : D
Question. A bacteriologist carries out his first attempt at engineering E.coli with the gene for human insulin. During the process, he realises that his stock of DNA ligase has depleted but decides to continue anyway. What is a likely consequence of his decision?
(a) Bacteria with the rDNA will not be able to form colonies in a fermenter.
(b) The resulting plasmids are not able to enter the E.coli bacteria even after applying heat shock.
(c) The resulting E.coli bacteria do not contain the human insulin gene.
(d) The bacterial plasmids do not have sticky ends and are unable to accommodate the human gene.
Answer : C
Question. To insert the insulin gene into bacterial DNA, both the bacterial plasmid and the human chromosome containing the insulin gene are treated with the same restriction enzyme. Using the same restriction enzyme ensures that
(a) DNA ligase is able to join the segments of human and bacterial DNA
(b) the exact length of nucleotides matching the insulin gene is removed from the plasmid
(c) both the bacterial and human DNA will contain sticky ends
(d) sticky ends in the cut plasmid and insulin gene are complementary.
Answer : D
Question. Identify A in the given figure.
(a) Polypeptide chain A
(b) Polypeptide chain B
(c) Polypeptide chain C
(d) None of these
Answer : D
Question. Why is the fermentor important for the production of human insulin by transgenic bacteria?
(a) It provides optimal conditions for the transgenic to multiply rapidly.
(b) It facilitates the extraction and purification of insulin from the transgenic bacteria.
(c) It maximise the rate of fermentation of the transgenic bacteria.
(d) It provides the low-oxygen conditions that are important for insulin production.
Answer : A
Assertion & Reasoning Based MCQs
For question numbers 51-60, two statements are given-one labelled Assertion and the other labelled Reason.
Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.
Question. Assertion : Agrobacterium tumefaciens is popular in genetic engineering because this bacterium is associated with the roots of all cereal and pulse crops.
Reason : Agrobacterium tumefaciens, is pathogen of several dicot plants is able to cause crown gall tumors. These tumors are incited by the conjugative transfer of DNA segment (T DNA).
Answer : D
Question. Assertion : PCR is routinely used for early diagnosis of HIV in suspected AIDS patients.
Reason : PCR can detect low amounts of DNA.
Answer : B
Question. Assertion : Mouse is the most preferred mammal for studies on gene transfers.
Reason : Mouse possesses features like short oestrous cycle and gestation period, relatively short generation time, production of several offspring per pregnancy, etc.
Answer : A
Question. Assertion : Transgenic food may cause toxicity or produce allergy.
Reason : Transgenic plants have high nutrient content.
Answer : B
Question. Assertion : Agrobacterium tumefaciens is called natural genetic engineer.
Reason : Agrobacterium tumefaciens infects all broad-leaved agricultural crops but does not infect cereal crops.
Answer : B
Very Short Answer Type Questions
Question. What is a patent ?
Answer : A patent is the right granted by a government to an inventor to prevent others from commercial use of his/her invention.
Question. What is gene therapy?
Answer : Gene therapy is the technique of genetic engineering which involves replacement of a faulty gene by a normal healthy functional gene.
Question. Give the full form of SCID.
Answer : Severe combined immunodeficiency disease.
Question. Name the transgenic plant from which hirudin is extracted.
Answer : Brassica napus
Question. Biotechnologists refer to Agrobacterium tumefaciens as a natural genetic engineer of plants. Give reasons to support the statement.
Answer : Agrobacterium tumefaciens is called natural genetic engineer of plants because genes carried by its plasmid produce effect in several parts of the plant.
Question. Why do DNA fragments move towards the anode during gel electrophoresis ?
Answer : DNA fragments are negatively-charged.
Question. Name the technique that is used to alter the chemistry of genetic material (DNA, RNA) to obtain desired result.
Answer : Genetic Engineering / Biochemical Engineering / Biotechnology.
Question. By using which vector, the nematode specific genes were introduced into the tobacco host plant. R
Answer : By using Agrobacterium, the nematode specific genes were introduced into the tobacco host plant.
Question. Write down the correct order of steps in polymerase chain reaction (PCR).
Answer : A single PCR amplification cycle involves three basic steps : denaturation, annealing and extension. PCR stands for a polymerase chain reaction in which multiple copies of the DNA segment, or gene of interest is synthesised in vitro.
Question. How the introduction of an alien DNA into plant host cell is achieved ?
Answer : Introduction of an alien DNA into the plant host cell is achieved by using a gene gun, coated with gold or tungsten particles.
Question. Suggest a technique to a researcher who needs to separate fragments of DNA.
Answer : Gel electrophoresis is used to separate DNA fragments.
Short Answer Type Questions
Question. Name the most commonly used bioreactor in biotechnology labs. Mention the most essential components this bioreactor must have so as to provide the optimum conditions to the culture medium, resulting in production of large volume of desired product.
Answer : Stirred-type
Agitator system, O2 delivery system, foam control system, temperature control system, pH control system.
Question. Write the functions of the following in biotechnology.
(i) Polymerase chain reaction technique
(ii) Restriction endonucleases
(iii) Bacterium Thermus aquaticus.
Answer : (i) Multiple copies of gene of interest can be obtained.
(ii) They can cut DNA molecule at a particular point by recognizing a specific sequence of base pairs. Thus they are useful in forming recombinant DNA.
(iii) Thermus aquaticus is the source of Taqpolymerase which remains active during high temperature induces denaturation of DNA in PCR technique and therefore allows chain reaction to proceed.
Question. All cloning vectors do have a ‘selectable marker’. Describe its role in recombinant DNA-technology.
Answer : The role of a selectable marker in rDNA technology is to identify and distinguish the bacterial cells that have taken up the recombinant vector during the transformation process.
Question. (i) Explain the significance of ‘palindromic nucleotide sequence‘ in the formation of recombinant DNA.
(ii) Write the use of restriction endonuclease in the above process.
Answer : (i) The palindromic nucleotide sequence is the recognition (specific) sequence present both on the vector and on a desired / alien DNA for the action of the same (specific) restriction endonuclease to act upon.
(ii) Same restriction endonuclease binds to both the vector and the foreign DNA, cut each of the two strands of the double helix at specific points in their sugar-phosphate backbone of recognition sequence for restriction endonucleases / palindromic sequence of vector and foreign DNA, to cut strand a little away from the centre of the palindrome sites, creates overhanging stretches / sticky ends.
Question. How are DNA fragments visualised during gel electrophoresis ? What is elution ?
Answer : Separated DNA fragments stained with ethidium bromide, followed by exposure to UV radiations.
Removal of DNA bands from agarose gel, and its extraction from the gel is elution.
Question. Write the palindromic nucleotide sequence that EcoRI reads, and indicate the site of its action.
Answer : 5’ – G AATTC – 3’, 3’-CTTAAG 5 ’
Question. Explain with the help of an example
the relationship between restriction endonuclease and a palindromic nucleotide sequence.
Answer : Restriction endonuclease recognises a specific palindromic nucleotide sequence, in the DNA molecule. Restriction endonuclease cuts the strand of DNA a little away from the centre of palindromic nucleotide sequence but between the same two bases on the opposite strands, leaving single stranded portions at the end called sticky ends.
Question. How is continuous culture system maintained in bioreactors and why ?
Answer : Used medium is drained out from one side of the bioreactor and fresh medium is added from the other side.
This type of culturing method produces a larger biomass leading to higher yields (of desired protein).
Question. Why is the ‘insertional inactivation’ method to detect recombinant DNA preferred to ‘antibiotic resistance’ procedure?
Answer : The presence of a chromogenic substrate gives blue coloured colonies, in absence of an insert/ in non-transformants, presence of an insert (in the enzyme site), results into (insertional inactivation of the b-galactosidase) colonies which do not produce colour.
Antibiotic resistance method requires duplicate plating/cumbersome procedure.
Question. What is EcoRI ? How does EcoRI differ from an exonuclease ?
Answer : EcoRI is a restriction endonuclease enzyme.
Exonuclease removes nucleotides from the ends of DNA. ½
EcoRI makes cuts at a specific position within the DNA.
Question. Refer to the given figure and answer the following questions.
(a) Name the process shown in the given figure.
(b) Identify A to D in the given figure.
(c) Name the processes X and Y. Also mention the enzymes involved in both steps.
Answer : (a) The given figure shows the steps involved in recombinant DNA technology. (b) In the given figure, A is plasmid vector, B is cut plasmid, C is fragment of DNA containing gene of interest and D is recombinant DNA. (c) Process X is restriction digestion and Y is annealing. Enzymes involved in X and Y are restriction endonuclease and DNA ligase respectively.
Question. (a) Why are transgenic animals so called?
(b) Explain the role of transgenic animals in (i) vaccine safety and (ii) biological products with the help of an example each.
Answer : (a) Refer to answer 15. (b) (i) Genetically modified organisms such as mice are being formed for use in testing the safety of vaccines before they are used on human beings. Transgenic mice are being used to test the safety of the polio vaccine. (ii) Transgenic animals that produce useful biological products can be created by the introduction of the DNA segment (or gene) which code for a particular product such as human protein (a-1-antitrypsin) used to treat emphysema. Similar attempts are being made for treatment of phenylketonuria (PKU) and cystic fibrosis.
Question. Write the functions of
(a) cryIAc gene
(b) RNA interference (RNAi).
Answer : (a) cryIAc gene controls cotton bollworms in Bt cotton. (b) RNA interference (RNAi) takes place in all eukaryotic organisms as a method of cellular defense. This method involves silencing of a specific mRNA.
Question. Name the soil bacterium that produces a protein/chemical that is toxic to insect pests.
Show with example that these are encoded by different forms of the genes.
Answer : Soil bacterium Bacillus thuringiensis produces proteins that kill certain insects like lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes), etc., B. thuringiensis forms some protein crystals. These crystals contain a toxic insecticidal protein. This toxin does not kill the Bacillus (bacterium) because it exists as inactive protoxins in them. But, once an insect ingests the crystals, it is converted into an active form of toxin due to the alkaline pH of the alimentary canal that solubilises the crystals. The activated toxin binds to the surface of mid gut epithelial cells and creates pores which cause cell swelling and lysis and finally cause death of the insect. cry genes code for certain crystal (cry) proteins that are toxic to insect larvae. The genes cryIAc and cryIIAb control cotton bollworm. When these genes are introduced into cotton plants through genetic engineering, these plants become resistant to the attack of cotton bollworm.
Question. What are transgenic plants? Explain any two disadvantages of transgenic plants.
Answer : The plants in which foreign genes have been introduced through genetic engineering are called transgenic plants. Following are the disadvantages of transgenic plants : (i) Gene transfer to non-target species : Transgenic crop plants can crossbreed with weeds, resulting in the transfer of transgene. These “super weeds” can then be difficult to eradicate. Other non-transgenic crops can also get the transgenes by cross breed. (ii) Allergies : The transgenic food may cause toxicity or produce allergies to human beings. The enzyme produced by the antibiotic resistance gene can cause allergies, because it is a foreign protein.
Question. Two children, A and B aged 4 and 5 years respectively visited a hospital with a similar genetic disorder. The girl A was provided enzyme
replacement therapy and was advised to revisit periodically for further treatment. The girl,B was, however, given a therapy that did not require revisit for further treatment.
(a) Name the ailments the two girls were suffering from.
(b) Why did the treatment provided to girl A required repeated visits?
(c) How was the girl B cured permanently?
Answer : (a) Both the girls A and B were suffering from SCID (Severe Combined Immuno Deficiency) syndrome produced by the deficiency of enzyme Adenosine deaminase (ADA). (b) The treatment provided to girl A required repeated visits because enzyme replacement therapy is not permanent cure. This is because these patients do not have functional T-lymphocytes, therefore they cannot provide immune responses against invading pathogens. (c) The girl B was treated by the transplanted stem cells that are injected into the bloodstream. They will then become healthy white blood cells that replenish immune functions – essentially building a whole new, functional immune system for the girl B. The immune system regains complete function and hence girl B was permanently cured.
Question. (a) Name the deficiency for which first clinical gene therapy was given.
(b) Mention the cause and one cure for this deficiency.
Answer : (a) Adenosine deaminase (ADA) deficiency (b) Adenosine deaminase enzyme is necessary for the proper functioning of our immune system. ADA deficiency is caused by the defect in the gene coding for enzyme adenosine deaminase. The possible treatments that can be given to a patient exhibiting adenosine deaminase (ADA) deficiency are: (i) bone marrow transplantation (ii) enzyme replacement therapy.
Question. What are cry proteins? Name an organism that produces it. How has man exploited this protein to his benefit?
Answer : The bacterium Bacillus thuringiensis is a common soil bacterium which produces a protein toxin that kills certain insects. The toxin is a crystal (Cry) protein. There are several kinds of Cry proteins which are toxic to different groups of insects. The gene encoding Cry protein is called cry gene. Biotechnologists have been able to isolate the gene responsible for production of toxin and introduce it into a number of plants to produce genetically modified plants resistant to insects, e.g., Bt cotton (resistant to bollworm) and GM tobacco (resistant to hornworms).
Question. Name the nematode that damages the roots of tobacco plants. How is transgenic tobacco plant made resistant to nematode using biotechnology?
Answer : A nematode Meloidogyne incognita infects the roots of tobacco plants and causes a great reduction in yield. A novel strategy that was adopted to prevent this infection was based on the process of RNA interference (RNAi). RNA interference (RNAi) is the phenomenon of inhibiting activity of a gene by synthesis of RNA molecules complementary to the mRNA. The normal (in vivo synthesised) mRNA of a gene is said to be “sense” because it carries the codons that are “read” during translation. Normally, the complement to the mRNA “sense” strand will not contain a sequence of codons that can be translated to produce a functional protein; thus, this complementary strand is called “anti-sense RNA”. The antisense RNA and mRNA molecules will anneal to form duplex RNA molecules that can not be translated. Thus, the presence of anti-sense RNA will block translation of the mRNA of the affected gene. The source of this complementary RNA could be from an infection by viruses having RNA genomes or mobile genetic elements (transposons) that replicate via an RNA intermediate. Using Agrobacterium vectors, nematodespecific anti-sense genes are introduced into the host plant. The introduction of DNA produces anti-sense RNA in the host cells. The transgenic host plants expresses anti-sense RNA. As in consequence, nematode infestation fails in the transgenic plants because the complementary anti-sense RNA forms a double stranded RNA (ds RNA) which interferes or blocks the translation and thus, silences the mRNA of the nematode. The result was that the parasite could not survive in transgenic plant. In such way, the transgenic plant gets protected from the parasite.
Question. List advantages of genetically modified plants.
Answer : Advantages of genetically modified plants are as follows: (i) Genetically modified plants are resistant to (a) diseases resulting from viral, bacterial and fungal infections (b) pests, such as nematodes and insects and (c) pesticides. (ii) GM plants can tolerate adverse abiotic stresses such as cold, drought, salt, heat. (iii) GM plants show increased efficiency of mineral usage (this prevents early exhaustion of fertility of soil). (iv) GM plants have high nutritional value, e.g., vitamin A enriched rice. (v) Plants such as poplar (Populus) trees have been genetically engineered to clean up heavy pollution from contaminated soil. (vi) These plants helped to reduce post harvest losses, e.g., Flavr savr transgenic tomato.
Question. What is the full form of SCID? Mention the cure of this disorder. Mention any one point how SCID is different from AIDS.
Answer : SCID stands for severe combined immunodeficiency disease. The SCID patient has a defective gene for the enzyme adenosine deaminase. He/she lacks functional T-lymphocytes and therefore fails to fight with infecting pathogens. It can be cured by gene therapy. In SCID, the patient lacks functional T-lymphocytes and it is congenital while in AIDS only T-helper cells are destroyed by virus, but is not congenital.
Question. Explain enzyme- replacement therapy to treat adenosine deaminase deficiency. Mention two disadvantages of this procedure.
Answer : Adenosine deaminase (ADA) enzyme is crucial for the immune system to function. Its deficiency is caused due to the deletion of the gene for adenosine deaminase. In some patients, ADA deficiency can be cured by the bone marrow transplantation. It can be treated by enzyme replacement therapy, in which functional ADA is given to the patient by injection. Two disadvantages of enzyme replacement therapy are : (i) It is not permanent cure because the replacement patient of ADA deficiency do not have functional T-lymphocytes, they cannot provide immune responses against invading pathogens. (ii) It is a costly method.
Long Answer Type Questions
Question. Neeraj was having a debate with Mohit regarding the advantages and disadvantages of transgenic animals. Neeraj was of the view that production of transgenic animals violates the integrity of species and animals suffer from cruelty so, it is unethical. On the other hand, Mohit emphasised the benefits that transgenic animals provide to the human race in various fields especially medicine.
(a) How do transgenic animals benefit humans?
(b) List the ethical issues related with the production of transgenic animals.
Answer : (a) Benefits derived from transgenic animals are as follows: (i) They produce useful biological products, that can be created by introduction of portion of gene, which codes for a particular product such as human protein (a ‑1- antitrypsin) from transgenic sheep is used to treat emphysema. (ii) Transgenic mice are being developed for use in testing the safety of vaccine before they are used in humans. (iii) They carry genes which make them more sensitive to toxic substances than non-transgenic animals. They are then exposed to toxic substances and the effects are studied. (b) The ethical issues concerned with the production of transgenic animals include: (i) Introduction of a transgene from one species into another species violates the ‘integrity of species’. (ii) Transfer of human genes into animals (and vice-versa) dilutes the concept of ‘humanness’. (iii) When animals are used for production of pharmaceutical proteins, they are virtually reduced to the status of a ‘factory’. (iv) Use of animals in biotechnology causes great suffering to them. (v) It is disrespectful to living beings, and only exploits them for the benefit of human beings.
Question. Briefly explain the principle, procedure and the role of ELISA.
Answer : Enzyme-linked immunosorbent assay (ELISA) is a nonisotopic immunoassay. ELISA is based on the immunochemical principles of antigen antibody reaction. The stages of ELISA are summarized as follows: (i) The antibody against the protein to be determined is fixed on an inert solid such as polystyrene. The biological sample containing the protein to be estimated is applied on the antibody coated surface. The protein antibody complex is then reacted with a second protein specific antibody to which an enzyme is covalently linked. Peroxidase, amylase and alkaline phosphatase are commonly used. (ii) After washing the unbound antibody linked enzyme, the enzyme bound to the second antibody complex is assayed. The enzyme activity is determined by its action on a substrate to form a product (usually coloured). This is related to the concentration of the protein being estimated. ELISA is widely used for the determination of small quantities of proteins (hormones, antigens, antibodies) and other biological substances. The most commonly used pregnancy test for the detection of human chorionic gonadotropin (hCG) in urine is based on ELISA. ELISA is also been used for diagnosis of HIV viruses in AIDS patient.
Question. (i) Describe the different steps in one complete cycle of PCR.
(ii) State the purpose of such an amplified DNA sequence.
Answer : (i) Refer SATQ-II/ Q. 19.
(Same value points to be awarded in an explanation)
(ii) Purpose : Used to ligate with a vector for further cloning.
Detection of bacteria or virus by amplification of their DNA / detection of HIV in AIDS patient.
Detection of mutation in genes in suspected cancer patients.
Question. (a) Explain the different steps carried out in Polymerase Chain Reaction, and the specific roles of the enzymes used.
(b) Mention application of PCR in the field of
Answer : (a)
The enzyme used in PCR in the thermostable taq polemarase enzymes, obtained from a bacterium called Thermus aquaticus.
(b) In biotechnology : It is used to amplify a single or a few copies of a piece of DNA. The amplified fragment can be used to ligate with a vector for further cloning. This results in recombinant DNA (rDNA).
In Diagnostic : PCR is used to detect HIV in suspected AIDS patients. It is also used to detect mutations in genes in suspected cancer patients. It is a powerful technique used to
identify many other genetic disorders.
Question. (a) Why are engineered vectors preferred ?
(b) A vector is engineered with some features which help in cloning within the host cell. List the features and explain all of them.
Answer : (a) Engineered vectors help in the easy linking of foreign DNA and the selection of recombinants from non-recombinants.
(b) Following are the four features, which are required to facilitate cloning into a vector.
(i) Origin of replication (ori) : It is a sequence of DNA from where replication starts. Any piece of alien/foreign DNA when linked to it can be made to replicate within the host
cells. This sequence also controls the copy number of the linked DNA.
(ii) Selectable marker : They help in identifying and eliminating non-transformants and permitting the growth of the transformants.
Transformation is a process by which a piece of DNA is introduced in a host bacterium.
(iii) Cloning sites : The vector must have a few, preferable one recognition site to link the alien DNA, presence of a particular cloning/ recognition site enables the particular restriction enzyme to cut the vector DNA.
(iv) Size of Vector : It should be small as large molecules tend to breakdown during purification.