Please refer to Biotechnology Principles and Processes Class 12 Biology Important Questions with answers below. These solved questions for Chapter 11 Biotechnology Principles and Processes in NCERT Book for Class 12 Biology have been prepared based on the latest syllabus and examination guidelines issued by CBSE, NCERT, and KVS. Students should learn these solved problems properly as these will help them to get better marks in your class tests and examinations. You will also be able to understand how to write answers properly. Revise these questions and answers regularly. We have provided Notes for Class 12 Biology for all chapters in your textbooks.

Important Questions Class 12 Biology Chapter 11 Biotechnology Principles and Processes

All Biotechnology Principles and Processes Class 12 Biology Important Questions provided below have been prepared by expert teachers of Standard 12 Biology. Please learn them and let us know if you have any questions.

Case Based MCQs

Read the following passage and answer any four questions from 41 to 45 given below:
Rama lives in a society where a robbery occurred last night. Robbers came into the flat and murdered the old lady residing there. Police came and restricted the entry into the flat. They took samples from the room, where the dead body was found. While examining, they found that there is some blood and tissue in the nails of old lady. According to their observation, police filtered out their inspection to three suspects viz. servant, cook and milkman. Finally after two days of robbery, police caught the criminal. It was the old lady’s cook. Rama was amazed to see that how quickly police completed and shut the case. She asked the inspector that how they did it? The police man told her that it become possible due to the sample collected from the victim, that lead them to the criminal. The sample taken from nail scraping was amplified using PCR and then tested.

Question. In PCR, the temperature used to denature the DNA is about
(a) 76°C
(b) 25°C
(c) 95°C
(d) 40°C.
Answer : C

Question. Given below are steps of polymerase chain reaction. 

Select the option that correctly mention the sequence in which they occur.
(a) (ii) → (iii) → (i)
(b) (i) → (ii) → (iii)
(c) (iii) → (i) → (ii)
(d) (ii) → (i) → (iii)
Answer : A

Question. Which of the following statements regarding PCR is correct?
(a) Taq polymerase, which is isolated from bacterium Thermus aquaticus is stable at low temperature only.
(b) Wi th the help of DNA l igase, the complementary sticky ends of the DNA are joined to produce a rDNA.
(c) Since the sequence of primers are complementary to 5′ end of the template DNA, they anneal to it.
(d) DNA purified from the cell is precipitated by adding hot ethanol.
Answer : B

Question. Taq polymerase synthesises DNA region between the primers using
(a) Mg2+
(b) dNTPs
(c) DNA ligase
(d) both (a) and (b).
Answer : D

Question. What technique was used by the police to identify the criminal?
(a) DNA fingerprinting
(b) Gel electrophoresis 
(c) Molecular diagnosis
(d) Cloning
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 : Bacterial cells are made competent by treating them with specific concentration of a divalent cation.
Reason : Treatment of bacterial cell with a divalent cation increases the efficiency with which DNA enters the bacterium through pores in its cell wall.
Answer : A

Question. Assertion : The insertion of DNA fragment into pBR 322 plasmid using enzyme Pst I or Pvu I make ampicillin resistant gene non functional.
Reason : Bacterial cells containing recombinant pBR322 is unable to grow in the presence of ampicillin.
Answer : B

Question. Assertion : Vector DNA and foreign DNA are cut by same restriction endonuclease.
Reason : Digestion of vector DNA and foreign DNA with same enzyme produces complementary sticky ends.
Answer : A

Question. Assertion : Amplification of a gene of interest can be done by polymerase chain reaction.
Reason : It is possible to amplify DNA segment approximately 1 billion times within a span of one day.
Answer : B

Question. Assertion : In recombinant DNA technology, human genes are often transferred into bacteria (prokaryotes) or yeast (eukaryote).
Reason : Both bacteria and yeast multiply very fast to form huge populations which express the desired gene.
Answer : A

Very Short Answer Type Questions

Question. What are synthesising enzymes?
Answer : The enzymes that are used to synthesise DNA strands on suitable templates are called synthesising enzymes. They are of two types : DNA polymerase and reverse transcriptase.

Question. Name the host cells in which microinjection technique is used to introduce an alien DNA.
Answer : Microinjection technique is used to introduce an alien DNA directly into the nucleus of the animal host cells such as oocytes, eggs and embryo.

Question. What are the drawbacks of stirred tank bioreactors?
Answer : The main drawback of stirred-tank bioreactor is that it is relatively expensive to run, which is mainly due to high energy requirements.

Question. Mention the source of thermostable DNA polymerase.
Answer : Thermophilic bacterium Thermus aquaticus is the source of thermostable DNA Taq polymerase.

Question. During the isolation of DNA, how can you remove RNA and protein from the DNA solution?
Answer : RNA can be removed by treatment with ribonuclease whereas proteins can be removed by treatment with protease.

Short Answer Type Questions

Question. How does b-galactosidase coding sequence act as a selectable marker? Why is it a preferred selectable marker to antibiotic resistance genes? Explain.
Answer : Some genes called selectable markers help in selecting those host cells which contain the vectors and eliminating the non-transformants. b-galactosidase is an alternative selectable marker developed to differentiate recombinants and non-recombinants on the basis of their ability to produce colour in the presence of a chromogenic substance. A recombinant DNA is inserted in the coding sequence of an enzyme β-galactosidase. This causes inactivation of the enzyme which is called insertional inactivation. If the plasmid in the bacterium does not have an insert, the presence of a chromogenic substrate gives blue coloured colonies. Presence of insert results into insertional inactivation of the b-galactosidase and, therefore, the colonies do not produce any colour, these colonies are marked as recombinant colonies.
β-galactosidase is a preferred selectable marker to antibiotic resistance genes because due to inactivation of antibiotics, selection of recombinants becomes burdensome process as it requires simultaneous plating on two plates having different antibiotics. But by using b-galactosidase as selectable marker, we can select recombinants and non-recombinants on a single plate.

Question. What are bioreactors ? List five growth conditions that a bioreactor provides for obtaining the desired product.
Answer : A bioreactor is a device in which raw materials are biologically converted into specific products by microbes, plant/animal cells etc. These are used for food processing, fermentation, waste treatment, etc. 
Growth conditions that a bioreactor provides for obtaining the desired products are :
(i) Controlled environment for optimum product yield.
(ii) Aseptic fermentation for a number of days and prevention of escape of viable cells.
(iii) Adequate mixing and aeration for optimum growth and production, without damaging the microorganism.
(iv) Easy and dependable temperature control
(v) Facility of sampling.

Question. Name the source organism from which Ti plasmid is isolated. Explain the use of this plasmid in biotechnology.
Answer : Agrobacterium tumefaciens is a soil-inhabiting bacterium that may invade growing plants at the junction of root and stem, where it can cause a cancerous growth known as
a crown gall.

Question. Rearrange the following in the correct sequence to accomplish an important biotechnological reaction :
(i) Denaturation of ds-DNA
(ii) Chemically synthesised oligonucleotides
(iii) Primers
(iv) Complementary region of DNA
(v) Thermostable DNA polymerase (from Thermus aquaticus)
(vi) Nucleotides provided
(vii) Genomic DNA template
(viii) In vitro synthesis of copies of DNA of interest
(ix) Enzyme DNA-polymerase.
Answer : The correct sequence to accomplish biotechnological reaction is : 

Question. Give reasons why:
(a) DNA cannot pass into a host cell through the cell membrane.
(b) Proteases are added during isolation of DNA for genetic engineering.
(c) Single cloning site is preferred in a vector.
Answer : (a) DNA is a hydrophilic molecule, so it cannot pass into a host cell through cell membrane. The cell membrane consists of lipid bilayers that are generally impermeable to hydrophilic molecules.
(b) DNA is interwined with proteins like histones and RNA. To obtain purified DNA, proteases are added during isolation of DNA which convert proteins into amino acids. The purified DNA finally precipitates out after the addition of chilled ethanol.
(c) In order to link the alien DNA, the vector needs to have very few, preferably single, recognition sites for the commonly used restriction enzymes. Presence of more than one recognition sites within the vector will generate several fragments, which will complicate the gene cloning process.

Question. (a) Why must a cell be made ‘competent’ in biotechnology experiments? How does calcium ion help in doing so?
(b) State the role of ‘biolistic gun’ in biotechnology experiments.
Answer : (a) Competent host is essential for transformation with recombinant DNA. Since DNA is a hydrophilic molecule, it cannot pass through membranes, so the bacterial cells must be made capable to take up DNA i.e., made competent. This is done by treating them with a specific concentration of a divalent cations, such as calcium which increases the efficiency with which DNA enters the bacterium through pores in its cell wall. Recombinant DNA (rDNA) can then be forced into such cells by incubating the cells with recombinant DNA on ice, followed by placing them briefly at 42°C (heat shock), and then putting them back on ice. This enables the bacteria to take up the recombinant DNA. Other methods are:
(i) Microinjection : DNA is inserted through microneedles or micropipettes.
(ii) Electroporation : Electric impulse induce transient pores.
(iii) Gene gun or biolistic : DNA coated with microscopic pellets of gold or tungsten is shot with high velocity into target cells.
(b) Biolistic gun helps in the process of gene transfer into the host cell without using a vector. In biolistic method or gene gun method, tungsten or gold particles, coated with foreign DNA are bombarded into target cells at a very high velocity. This method is suitable for plants, but is also used to insert genes into animal that promote tissue repair into cells (particularly cancer of mouth) near wounds. It has made great impact in the field of vaccine development.

Question. Explain the importance of ( i ) ori,
(ii) ampR and (iii) rop in the E.coli vector shown below.   

Answer : (i) ori : ori is the origin of replication. This is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within host cells. It controls the copy number of the linked DNA.
(ii) ampR : Gene for ampicillin resistance which helps in selecting the transformants.
(iii) rop : rop codes for the proteins involved in the replication of the plasmid.

Question. Explain the role of Ti plasmids in biotechnology.
Answer : Agrobacterium tumefaciens is a soil-inhabiting bacterium that may invade growing plants at the junction of root and stem, where it can cause a cancerous growth known as a crown gall. A. tumefaciens contains Ti plasmid which carries gene for tumour formation for using Agrobacterium tumefaciens as a cloning vector researchers deleted the genes which governs auxin and cytokinin production (the oncogene) from T-DNA of Ti plasmid, it is known as disarming. After disarming, this T-DNA is inserted into chromosomes of the host plant where it produces copies of itself.

Question. (a) Mention the difference in the mode of action of exonuclease and endonuclease.
(b) How does restriction endonuclease function?
Answer : (a) Differences between action of exonucleases and endonucleases are as follows :    

(b) Restriction nucleases act as molecular scissors or chemical scalpels. Each restriction endonuclease functions by ‘inspecting’ the length of a DNA sequence. Once it finds its specific recognition sequence, it will bind to the DNA and cut each of the two strands of the double helix at specific points in their sugar-phosphate backbones. Each restriction endonuclease recognises a specific palindromic nucleotide sequence in the DNA.

Question. Name the technique to obtain multiple copies, of a DNA segment of interest, synthesized in vitro. Name two sets of primers that are necessary for reaction to occur. Mention three diagnostic applications of this technique.
Answer : PCR (Polymerase Chain Reaction). The two sets of primers (small chemically synthesised oligonucleotides that are complementary to the regions of DNA) are required in each cycle of polymerase chain reaction. Primers hybridise to target DNA region and allow synthesis of the DNA towards one another whereas DNA polymerase synthesise DNA region between the primers using dNTPs and Mg2+. Three diagnostic applications of PCR are :
(i) Diagnosis of pathogens
(ii) Diagnosis of specific mutations
(iii) Prenatal diagnosis

Question. Why is ‘plasmid’ an important tool in biotechnology experiments?
Answer : Plasmid have the ability to replicate within bacterial cells independent of the control of chromosomal DNA and have high copy number, therefore any alien DNA ligated to it, also multiplies to equal the copy number of plasmids. So, it is used as a vector in gene cloning experiments and thus, plays a role of an important tool in biotechnology.

Question. (a) What is EcoRI? What does ‘R’ represent in this?
(b) Give the palindromic nucleotide sequence recognised by it.
(c) Explain its action.
Answer : (a) Enzyme EcoRI is named as follows :
The capital letter E comes from the genus Escherichia. The letters co are derived from the species name coli. The letter R is from RYI3 (strain). The Roman number I indicates that it
was the first enzyme isolated from the bacterium E. coli RYI3.
(b) EcoRI is a restriction endonuclease enzyme it recognises base sequences
5′-GAATTC-3′
3′-CTTAAG-5′ in DNA duplex.
(c) It cut each of the two strands between G and A producing sticky ends.

Question. Read the following base sequence of a certain DNA strand and answer the questions that follow:   

(i) What is called a ‘palindromic sequence’ in a DNA ? 
(ii) Write the palindromic nucleotide sequence shown in the DNA strand given and mention theenzyme that will recognise such a sequence.
(iii) State the significance of enzymes that identify palindromic nucleotide sequences.
Answer : (i) The palindromic sequence in DNA is a sequence of base pairs that reads same on the two strands when orientation of reading is kept the same.
(ii) The palindrome sequence in the given DNA strand is :
GAATTC CTTAAG
This is the recognition sequence for restriction enzyme EcoRI.
(iii) Each restriction endonucleases recognise a specific palindromic nucleotide sequences in the DNA. Restriction enzymes cut the strand of DNA a little away from the centre of the palindrome sites, but between the same two bases on the opposite strands. This leaves single stranded portions at the ends. These are overhanging stretches called sticky ends on each strand. These are named so because they form hydrogen bonds with their complementary cut counterparts. This stickiness of the ends facilitates the action of the enzyme DNA ligase.

Long Answer Type Questions

Question. What is cloning vector ? Why is it used ?
Explain the technique of using such a vector in E.coli.
Answer : The cloning vectors are DNA molecules that can carry a foreign DNA segment and replicate inside the host cell. These are plasmids, cosmids, phagemids, yeast artificial chromosome (YAC), bacterial artificial chromosome (BAC), transposons and virus. Cloning vector carry rDNA and they generally have high copy number, they can produce multiple number of required gene. Vectors help in easy linking of foreign DNA and in selection of recombinants from non recombinants. The entire procedure of gene cloning or recombinant DNA technology may be classified into the following six steps for the convenience in description and on the basis of the chief activity performed.
(i) Production and isolation of the DNA fragments to be cloned.
(ii) Insertion of the isolated gene in a suitable vector to obtain recombinant DNA.
(iii) Introduction of the recombinant DNA into a suitable organism/cell (usually E.coli) called host (transformation).
(iv) Selection of the transformed host cells, and identification of the clone containing the desired gene/DNA fragment.
(v) Multiplication/expression of the introduced gene in the host.