Biotechnology Principles and Processes VBQs Class 12 Biology

VBQs for Class 12

VBQs Biotechnology Principles and Processes Class 12 Biology with solutions has been provided below for standard students. We have provided chapter wise VBQ for Class 12 Biology with solutions. The following Biotechnology Principles and Processes Class 12 Biology value based questions with answers will come in your exams. Students should understand the concepts and learn the solved cased based VBQs provided below. This will help you to get better marks in class 12 examinations.

Biotechnology Principles and Processes VBQs Class 12 Biology

Very Short Answer Type Questions

Question. Suggest a technique to a researcher who needs to separate fragments of DNA.
Answer :
Gel electrophoresis is used to separate DNA fragments.

Question. Mention the use of gel electrophoresis in biotechnology experiments.
Answer :
Cut fragments of DNA can be segregated / separated. 

Question. Why it is not possible for an alien DNA to become part of a chromosome anywhere along its length and replicate normally ?
Answer :
Alien DNA must be linked to ori / origin of replication / site to start replication.
Detailed Answer :
This is because the alien piece of DNA has to become part of a chromosome, which has the ability to replicate. In a chromosome there is a specific DNA sequence called the origin of replication, Ori which is responsible for initiating replication. 

Question. Write the two components of the first artificial recombinant DNA molecule constructed by Cohen and Boyer. 
Answer :
Restriction enzyme and vector. 

Question. State what happens when an alien gene is ligated at the Sal I site of pBR322 plasmid.
Answer :
When an alien gene is ligated at the Sal I site of tetracycline resistance gene in the vector pBR322, the recombinant lose tetracycline resistance due to insertion of the foreign DNA. 

Question. Why is ’plasmid’ an important tool in biotechnology experiments ?
Answer :
Plasmids are commonly used to multiply or express particular genes and act as vectors to transfer piece of foreign DNA attached to them.

Question. Which main technique and instrument is used to isolate DNA from a plant cell ?
Answer :
Centrifugation and centrifuge. 

Question. Why do DNA fragments move towards the anode during gel electrophoresis ?
Answer :
DNA fragments are negatively charged. 
Detailed Answer:
In gel electrophoresis, DNA fragments are negatively charged molecules. They can be separated by forcing them to move towards the anode under electric field through a medium / matrix.

Question. Write the palindromic sequence that EcoRI recognises.
Answer :
Palindromic sequence is asked, write both the sequence with polarity.

Question. Mention the role of Restriction Enzymes in Recombinant DNA technology.
Answer :
To cut DNA at specific sites / Molecular scissors (DNA). 

Question. Name the specific sequence of DNA in a plasmid that the gene of interest ligates with to enable it to replicate. 
Answer :
Origin of replication (Ori). 

Question. Explain giving reasons why an alien piece of DNA needs to be integrated to a specific sequence of host DNA for its cloning ?
Answer : Ori (origin of replication) is the specific DNA sequence where the replication of DNA is initiated.
Therefore for multiplication of alien DNA in the host it has to be integrated to the ori (origin of replication). 

Short Answer Type Questions

Question. Why are molecular scissors so called ? Write their use in biotechnology. 
Answer :
The restriction enzymes are known as molecular scissors as they cut the DNA at specific sites or locations.
They help (in genetic engineering) to form recombinant molecules of DNA, which are composed of DNA from different genomes.

Question. How does a restriction nuclease function ? Explain. 
Answer :
Restriction nuclease cut DNA at specific sites.
Exonuclease cuts DNA at the ends, endonuclease cuts at specific position within DNA. 
Restriction endonuclease cuts the DNA at specific palindromic sequence. 

Question. Write the role of ‘Ori’ and ‘restriction’ site in a cloning vector pBR322. 
Answer :
Ori : It is a genetic sequence that acts as the initiation site for replication of DNA. Any fragment of DNA, when linked to the ori region, can be initiated to replicate.
Restriction site : It is the recognition site for restriction enzymes (such as EcoRI, Hind III, Pvu I and Bam Hl). Recognition sites are the genetic sequences from where the restriction enzymes cut the DNA.

Question. Explain the work carried out by Cohen and Boyer that contributed immensely to biotechnology.
Answer :
Cohen and Boyer invented the technique of DNA Cloning and conducted first genetic engineering experiments. They conducted experiment on removing plasmid from one bacterial cell and reinserting into another bacterial cell.

Question. State the role of DNA ligase in biotechnology.
Answer :
The role of DNA ligase in biotechnology is to join two different restricted fragments of DNA to make recombinant DNA. the DNA fragments are joined from their ends. 

Question. State how has Agrobacterium tumefaciens been made a useful cloning vector to transfer DNA to plant cells. 
Answer :
Agrobacterium tumefaciens has Ti plasmid. This plasmid is modified into a cloning vector, which is no more pathogenic to host plants and is able to deliver genes of interest. 

Question. Describe a palindrome with the help of an example. 
Answer : 
A DNA sequence that reads the same, on the two strands from 5’- 3’ direction or 3′ → 5′ direction. 

Question. (i) Why must a cell be made ‘competent’ in biotechnology experiments ? How does calcium ion help in doing so ?
(ii) State the role of ‘biolistic gun’ in biotechnology experiments.
Answer :
 (i) (a) To take up the (hydrophilic) DNA from the external medium. 
(b) Divalent calcium ions increase the efficiency of the cell to take up foreign DNA through pores in the cell wall. 
(ii) To introduce alien DNA into the plant cell by bombarding them with high velocity microparticles (gold or tungsten coated with DNA). 
Detailed Answer :
(i) In biotechnology experiments, the cells must be made competent so that they can take up the hydrophilic DNA molecule inside them from the external medium. Treatment of bacterial cells with divalent calcium cations makes them competent and helps them to take up the DNA through the pores in the cell wall.
(ii) Biolistic gene or gene gun is a method of introducing alien DNA into the plants cells. In this method, the host cells are bombarded with high velocity micro-particles of gold or tungsten coated with DNA molecules.

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. 

Biotechnology Principles and Processes VBQs Class 12 Biology

(No mark, if polarity is not shown or if only one strand is shown).

Question. Explain the role of the enzyme EcoRI in recombinant DNA technology.
Answer :
 EcoRI (Restriction endonuclease) acts as molecular scissors. They serve as tools for cutting DNA molecule at specific palindromic sites, inspects length of DNA and recognises specific palindromic nucleotide sequence, binds with DNA, cuts each of the two strands of double helix at specific points. 

Question. (i) Draw the figure of vector pBR322 and label the following :
Origin of replication
Ampicillin resistance site
Tetracycline resistance site
Bam H1 restriction site.
(ii) Identify the significance of origin of replication.
Answer : (i)

Biotechnology Principles and Processes VBQs Class 12 Biology

(ii) Origin of replication is responsible for controlling the copy number of the DNA sequence inserted. 
Carefully draw the diagram and label the asked parts carefully. Each labeling carries a mark.

Question. Explain the basis on which the gel electrophoresis technique works. Write any two ways the products obtained through this technique can be utilized.
Answer :
 Basis of technique : Since DNA fragments are negatively charged, they can be separated by forcing them to move towards the anode under an electric field through a medium of matrix (agarose).
Uses : (i) The purified DNA fragments are obtained by gel electrophoresis.
(ii) They are used in DNA fingerprinting. 

Question. How are the following used in biotechnology ?
(i) plasmid-DNA.
(ii) recognition sequence.
(iii) gel electrophoresis.
Answer :
 (i) Plasmids are relatively small DNA sequences that can self replicate and exist independent of the chromosome. Plasmids often carry antibiotic resistance genes that makes them selectable.
They can be genetically modified – cut at specific locations using restriction enzymes and new DNA sequences are included. This recombinant plasmid is reintroduced into bacteria and easily forced to multiply in large numbers at relatively low cost.
Thus, plasmids have been used in biotechnology to develop vectors (tools) for basic research like studying new genes as well as to produce therapeutic chemicals.
(ii) The restriction enzymes cut the DNA at a specific point called recognition sequence or sites. Each restriction enzyme has its particular restriction site. Thus, recognition sequences play a vital role in giving direction to the restriction enzymes regarding the particular position of cleavage in the DNA.
(iii) Gel electrophoresis is a technique used to separate DNA fragments according to their size. DNA fragments are negatively charged, so they move towards the positive electrode.
Because all DNA fragments have the same amount of charge per mass, small fragments move through the gel faster than larger ones.
When a gel is stained with a DNA-binding dye, the DNA fragments can be seen as bands, each representing a group of same-sized DNA fragments. 

Question. Eco RI is used to cut a segment of foreign DNA and that of a vector DNA to form a recombinant DNA. Show with the help of schematic diagrams.
Answer :

Biotechnology Principles and Processes VBQs Class 12 Biology

Question. Explain the role(s) of the following in Biotechnology : 
(i) Restriction endonuclease
(ii) Gel – electrophoresis
(iii) Selectable markers in pBR322.
Answer :
(i) Cuts at specific position within the DNA
/ cuts DNA at specific nucleotide / cuts at palindromic nucleotide sequence. 
(ii) Separation of DNA fragments (under the influence of electric field). 
(iii) Helps in identifying and eliminating nontransformants from transformants / selection of transformants. 
Detailed Answer :
(i) The enzyme restriction endonuclease recognise the base sequence at palindrome sites in DNA and cut it’s strand.
(ii) Gel-electrophoresis is a technique of separation of charged molecules under the influence of an electric field. With the help of gel electrophoresis technique, DNA fragments get separated according to size through the pores of agarose gel.
(iii) Selectable marker (marker gene) helps to select the transformants and eliminate the nontransformants.

Question. (i) Why must bacterial cells be first made ‘competent‘ in r-DNA technology ? How is this process carried out? [KVS]
(ii) Name the method by which an alien DNA can be made to enter (a) plant cell; (b) animal cell.
Answer :
(i) Since DNA is hydrophilic, it cannot pass through cell membrane, hence bacterial cells are made competent. 
By treatment with a specific concentration of a divalent cations, such as Ca++ which increases efficiency of entry of DNA through the pores of cell wall. 
(ii) (a) Plant cells – biolistic / gene guns 
(b) Animal cells – Micro injection 
Detailed Answer:
(i) DNA is a hydrophilic molecule, so it cannot pass through cell membrane. To avoid this problem, bacterial cells are treated with a specific concentration of a divalent cations (e.g., calcium), so as to increase the pore size in the cell wall. As a result, DNA enters the bacterium through pores of cell wall.
(ii) Other methods to introduce alien DNA into host cell are :
(a) Plant cell : Biolistics (gene gun) method.
(b) Animal cell : Micro – injection.

Question. Draw a diagram of a typical agarose gel electrophoresis showing migration of undigested and digested sets of DNA fragments. Label (a) the digested and undigested DNA fragments, (b) Anode and cathod ends of the plate. Mention the role of electrophoresis in biotechnology.
Answer :

Biotechnology Principles and Processes VBQs Class 12 Biology

The cutting of DNA by restiction endonuclease results in fragments of DNA. These fragments can then be separated by (Gel) electrophoresis. 

Question. (a) How do DNA fragments migrate and resolve in a Gel electrophoresis?
(b) How lane one is different from lane 2, 3 and 4 in the Gel electrophoresis set up?
(c) How pure DNA fragments are made observable in the visible light?

Biotechnology Principles and Processes VBQs Class 12 Biology

Answer : (a) The DNA fragments resolve according to their size through sieving effect provided by the agarose gel. Hence, the smaller the fragment size, the farther it moves. 
(b) The given agarose gel electrophoresis shows migration of undigested DNA fragments in lane 1 and digested set of DNA fragments in lane 2 to 4. 
(c) The separated DNA fragments can be visualized only after staining the DNA with a compound known as ethidium bromide followed by exposure to UV radiation. 

Long Answer Type Questions

Question. (i) Describe the characteristics a cloning vector must possess.
(ii) Why DNA cannot pass through the cell membrane ?
Explain. How is a bacterial cell made ‘competent’ to take up recombinant DNA from the medium ?
Answer :
 (i) (a) Should have ori / origin of replication, Has selectable marker, genes encoding for an antibiotic resistance / genes encoding for β-galactosidase (b) Has cloning site / recognition site, for the restriction enzyme to recognise.
(ii) DNA is a hydrophilic molecule.
Bacterial cell is made competent by treating with specific concentration of Ca++ ions / divalent ions, incubating them on ice, heat shock for a short period and placing it back once again. 
Detailed Answer :
(i) The following are the features that are required to facilitate cloning into a vector :
(a) Origin of replication (ori) : This is a sequence from where replication starts and any piece of DNA when linked to this sequence can be made to replicate within the host cells. This sequence is also responsible for controlling the copy number of the linked DNA.
(b) Selectable marker : The vector requires a selectable marker, which helps in identifying and eliminating non transformants and selectively permitting the growth of the transformants. Transformation is a procedure through which a piece of DNA is introduced in a host bacterium. Normally, the genes encoding resistance to antibiotics such as ampicillin, chloramphenicol, tetracycline or kanamycin, etc. are considered useful selectable markers for E. coli.
(c) Cloning sites : In order to link the alien DNA, the vector needs to have very few 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.