Important questions class 12 biology chapter 11

Important Questions Class 12 Biology Chapter 11

Important Questions for CBSE Class 12 Biology Chapter 11 – Biotechnology: Principles and Processes:

Class 12 Biology Chapter 11 Important Questions cover the broad field of biotechnology which entails employing technology to exploit living things in order to create goods that would promote human welfare.

With these Class 12 Biology Chapter 11 Important Questions, students will come to know the two basic methods that gave rise to contemporary biotechnology are genetic engineering and bioprocess engineering.

Moreover, with these Class 12 Biology Chapter 11 Important Questions, Extramarks will provide students with detailed and authentic solutions to important questions. 

CBSE Class 12 Biology Chapter-11 Important Questions

Study Important Questions for CBSE Class 12 Biology Chapter 11 – Biotechnology: Principles and Processes 

1. DNA is broken down into pieces by a restriction enzyme. Name the procedure used to monitor this enzyme’s activity and segregate DNA fragments.

Ans: Gel electrophoresis is a method used to separate DNA fragments after DNA has been broken down by a restriction enzyme and formed into fragments.

2. List two vectors that are often employed in genetic engineering.

Ans: Plasmid, as well as Bacteriophage, are just the two most often utilised vectors in genetic engineering.

3. In genetic engineering, certain enzymes are regarded as molecular scissors. What moniker do these enzymes go by?

Ans: Restrictions in genetic engineering enzymes are also the enzymes that break down DNA strands into pieces, which is why they are referred to as molecular scissors.

4. Describe EcoRI’s standard terminology.

The answer is a bacterium called E. Escherichia, where co represents E. coli, R for the name of Strain, and I for order of Isolation of enzymes from bacterial strain.

5. A plasmid and a DNA molecule fragment both have three EcoRI restriction sites. How many pieces of linear DNA as well as plasmid will be generated, respectively?

Answer: After being broken down by a restriction enzyme, linear DNA will result in 4 pieces, whereas plasmids would result in 6 fragments.

6. To transfer the desired gene into the host cell, a bacterium’s circular extrachromosomal DNA segment is employed. What name has it been given?

Ans: In bacteria, a plasmid is a circular DNA fragment that is not part of the chromosome.

7. Identify the material that serves as a medium in gel electrophoresis.

Ans: Agarose will be a material that is employed as a medium in gel electrophoresis.

8. What does bioconversion mean?

Ans: Bioconversion is the process of transforming raw material into usable products with the aid of diverse elements, such as microbial, plant, or animal cells.

9. Which species of bacteria produces thermostable DNA polymerase?

Answer: A bacteria called thermus aquaticus may be used to create thermostable DNA polymerase.

10. What technology is used to amplify DNA?

This polymerase chain reaction is a method that may be used to amplify DNA.

Very Short Answer Questions (1 Mark)

1. Who was the first to identify restriction enzymes?

Ans: Warner Arber and Hamilton-Smith were the ones to discover the restriction enzymes.

2. Why are restriction enzymes absent from eukaryotic cells?

Ans: The DNA in eukaryotic cells is found to be extensively methylated, which prevents restriction enzymes from being present.

3. Explain why DNA in a gel electrophoresis procedure travels toward the anode.

Ans: The DNA is discovered to be flowing towards the anode inside the gel electrophoresis because it is negatively charged as a result of a phosphate group, which causes the migration of DNA more toward the anode.

4. Which enzymes are dubbed “molecular scissors”? 

Ans: The enzymes known as restriction endonucleases are also known as molecular scissors because they cut DNA strands into pieces as a result of their digestion.

5. What is the common vector for plant cell transformation?

Ans: Agrobacterium tumefacient is the name of the widely used vector that causes transformation in plant cells.

6. What enzyme removes the 5 phosphate group of nucleic acid, and what is its name?

Ans: Alkaline phosphates are also the proteins in charge of removing the phosphate group of nucleic acid.

Short Answer Questions (2 Marks)

These are references to CBSE extra questions, CBSE revision notes, and CBSE sample papers from the CBSE syllabus. To secure good marks, students can also refer to CBSE’s past years’ question papers.

1. Identify the two primary processes that make up the upstreaming process. What makes this procedure important?

Ans: The upstreaming process involves selecting a microbial strain that can synthesise a certain product with the appropriate commercial value. This strain is then exposed to improvement techniques in order to maximise the strain’s ability to synthesise inexpensive amounts of the product. The fermentation process, which is often carried out in enormous tanks known as fermenters or bioreactors, is included in the upstream phase.

2. Name two different groups of restriction enzymes. Put forward their assigned duties.

Ans: There are two groups of restriction enzymes: exonucleases and endonucleases.

While endonucleases play a significant role in cutting DNA at specific places between both ends of DNA, exonucleases are responsible for removing nucleotides from the endpoints of DNA.

3. Describe any two of the restriction endonuclease enzymes’ characteristics.

Ans: The restriction of endonuclease enzymes’ characteristics are as follows.

(I) After examining the extent of the DNA sequence, the restriction enzyme enzymes connect at the DNA’s recognition sequence.

(ii) Its job is to make particular cuts in the sugar-phosphate backbone.

4. What do you mean by “selectable markers”? Why are they necessary for genetic engineering?

Ans: A gene known as a genetic marker that causes the removal of the non-transformant can be used to choose the host cells which carry the vector. It is employed in genetic engineering, for instance, where the gene that codes for antibiotic resistance is proven to be a helpful selectable marker because when it inserts into a cell, it only allows transformants to develop.

Short Answer Questions (3 marks) 

• Write down the precise location in the palindrome as well as the bond that EcoRl cuts.

Ans: Limited endonuclease of the DNA is cut by EcoRI at the GAA TTC palindromic region, which is a well-known DNA sequence. The phosphodiester bond between G and A on the bases of the palindrome is the type of bond that EcoRI breaks named as Restrictions site.

• During bacterial transformation, a gene was ligated to the plasmid vector to create a recombinant DNA. Inadvertently, an exonuclease was put in the tube. What impact will it have on the experiment’s next stage?

Ans: The experiment won’t be affected. This is due to recombinant DNA’s closed, circular shape and lack of free ends. Exonuclease won’t destroy the DNA as a result.

• An agarose gel was used to run a mixture of the fragmented DNA. Ethidium bromide was used to stain the gel, but no bands could be seen. What might be the reason?

These factors could be to blame for the following reasons.

• • Nucleases must have broken down the DNA.
  • In the gel assembly, the electrodes are positioned in a reverse manner. As a result, the DNA molecules leave the gel.
  • Perhaps not enough ethidium bromide was injected, making DNA invisible.
• What would happen if a cloning vector was a plasmid without a selectable marker?

Ans: To identify transformed cells from non-transformed cells, a selectable marker is used. It would be challenging to choose the transformants if the cloning vector lacked a selectable marker.

• What part does Agrobacterium tumefaciens play in the transformation of plants?

Ans: The plant pathogen Agrobacterium tumefaciens affects a variety of crops, including tomato, sunflower, cotton, soybean, and others. It produces crown gall disease in plants that have been exposed to the Ti plasmid or the plasmid that induces tumours. The T-DNA is a DNA fragment that the Ti plasmid inserts into the host plant cell’s DNA. Tumours are caused by this T-DNA.

• Describe a bioreactor. Describe the various types of bioreactors.

A large container called a bioreactor is used to carry out biological reactions and cultivate aerobic cells for cellular or enzymatic immobilizations. The various kinds of bioreactors include the following.

• • Bubble Column Bioreactors
  • Packed Bed Bioreactors
  • Airlift Bioreactors
  • Stirred Tank Bioreactors
  • Fluidized Bed Bioreactors
• Mention three vector-free techniques that can be utilised to transfer recombinant DNA into a ready host cell.

The three vector-free techniques are as follows.

• • Bacteria directly ingest environmental genetic material through a process known as transformation. For this, calcium chloride is applied to the bacterial cells. The cells are then heated to a very high temperature after being incubated in ice. As a result, the bacterial cell wall becomes porous, allowing the bacterial cell to absorb the foreign DNA.
  • Microinjection: Using a microneedle, recombinant DNA is directly injected into the animal cell’s nucleus in this procedure.
  • Biolistics/Gene Gun Method: DNA-coated gold and tungsten microparticles are fired at the cells at extremely high speeds.
• Why is it impossible for alien DNA to join a chromosome anywhere along its length and carry out regular replication?

Ans: The origin of replication in a chromosome serves as the starting point of replication as it helps DNA polymerase bind, whereas alien DNA cannot multiply and replicate on its own and needs a certain sequence to do so.

• Why is the term “plasmid” crucial in biotechnology experiments?

Ans: In bacterial cells, plasmids can multiply without the help of chromosomal DNA. Due to their large copy number, any foreign DNA joined to them will have an identical copy number to plasmids. As a result, it serves as a crucial tool in biotechnology and is utilised as a vector in gene cloning operations.

• Agrobacterium tumefaciens is referred to as a natural plant genetic engineer by biotechnologists. Give arguments in favour of the claim.

Ans: Numerous dicot plants are infected by the pathogen Agrobacterium tumefaciens. Because it can transfer a fragment of its DNA (known as T-DNA) to turn regular plant cells into tumour cells, it is employed as a natural genetic engineer. It instructs the tumour cells to create the substances the infection needs.

• The enzyme ß-galactosidase is regarded as a more reliable selective marker. Justify this assertion. 

Ans: While the selection of recombinants due to antibiotic resistance gene inactivation is a laborious and time-consuming process, growing them simultaneously on two antibiotics-containing media, the coding sequence of p-galactosidase is a better maker because the recombinants and non-recombinants are differentiated based on their ability to generate colour within the presence of a chromogenic substrate.

•  Explain the EcoRI mode of action. 

Ans: In order to work, restriction nucleases first check the length of the DNA sequence, bind to particular recognition sequences, and then cut the strands at the sugar-phosphate backbones.

There are two different sorts of these nucleases based on how they work.

• • DNA’s terminal ends have sequences that restrict exonuclease cut.
  • Cuts between the two bases of the recognition sequence are made by restriction endonucleases like EcoRI.
•  Give a good example to illustrate how to name a restriction endonuclease.

Ans: The following regulations apply to the naming of restriction endonuclease.

• • The genus and species of the prokaryotic cell from which enzymes are extracted are represented by the first and second letters of the enzyme, respectively.
  • The order in which the enzymes were separated from the bacterial strain is indicated by the Roman numbers that follow the name. For instance, EcoRI comes from Escherichia coli strain RY13, Hind II from strain Rd of Haemophilus influenzae, etc.
•  How does a DNA strand get sticky ends? Why do they go by that name?
  • Restriction endonucleases are the enzymes that cause DNA to generate sticky ends. These enzymes split the DNA strand between the identical two bases on both strands, but slightly away from the palindrome sequence’s centre.

• • This causes both of the complementary strands to have single-stranded lengths at their ends. Due to their ability to create hydrogen bonds with the corresponding base pair sequences, these overhanging lengths are known as sticky ends.
• How is the distinction between recombinants and non-recombinants made using the selectable marker of insertional inactivation of an enzyme?

Ans: By putting the desired gene in the coding region of the enzyme, such as ß-galactosidase, the desired gene causes the enzyme to become active. In recombinants, it causes the ß-galactosidase gene to become inactive. As a result, when grown on a chromogenic substrate, the recombinant or modified hosts are unable to create any colour. In order to distinguish recombinants from non-recombinants, ß-galactosidase serves as a selectable marker.

Long Answer Questions (5 Marks)

1. To generate huge amounts of items, bioreactor development is necessary. State what are the ideal growing conditions for bioreactors.

Ans: A bioreactor is a device that has the shape of a vessel and contains different organisms or chemical compounds that go through chemical reactions to produce biologically active molecules. It is necessary to maintain the optimal temperature, pH, substrates, salts, vitamins, plus oxygen levels in order to create the best growth of the desired product.

2. What are the differences between a sparged stirred tank bioreactor and a merely stirred tank bioreactor?

Ans: In a sparged stirred-tank bioreactor, the air is discovered to be bubbled, which prevents adequate mixing throughout the reactor. In a simply stirred tank bioreactor, the stirrer allows even mixing and availability of oxygen throughout the process.

3. What is the PCR technique? What are the many phases in this approach described?

Ans: A polymerase chain reaction is a technique used for producing millions of copies of DNA from a single DNA sample. Primers, which are brief segments of single-stranded DNA that have a consensus sequence to the DNA Template, and DNA polymerase are its two key reagents. Taq polymerase, which is taken from the bacterium Thermus aquatics, is a heat-stable DNA polymerase. There are three steps in each cycle.

a) DENATURATION: In the first phase, a procedure known as macromolecule denaturation causes the two strands of the DNA helix to physically separate at a heat.

b) RENATURATION/ANNEALING: The temperature is decreased in the second stage to allow the primers to bind to the DNA’s complementary sequences.

d) ANNULATION: The third stage involves synthesising copies of the target sequence of DNA via primer extension. The heat has increased to 750 c. Taq-polymerase starts DNA synthesis just at the primer’s 3-OH end at this temperature.

4. Why are they called molecular scissors? Write about how biotechnology uses them.

Ans: Because they cut DNA at specific base-pair sequences, molecular scissors are so named. DNA is cut at certain locations by molecular scissors or restriction enzymes, which also produce sticky ends that make it easier for the DNA to link with the host genome or a DNA vector. They are crucial to biotechnology or genetic engineering. It’s because we can snip the desired gene with the aid of these enzymes and insert it into expression vectors.

5. Why and how is it possible to “compete” bacteria?

Ans: DNA molecules cannot cross cell membranes because they are hydrophilic. Recombinant DNA must be injected into the cell in order for it to be integrated into the vector or host genome. Therefore, in biotechnology experiments, the host cells must be made competent.

Cells can be trained in two different ways to accept DNA:

• Chemical process: A certain concentration of a divalent cation, such as calcium, is administered to the host cell in order to enlarge the pore size of the cell membrane. The effectiveness of DNA to enter treated bacterial cells through cell wall pores is increased by incubating DNA with it at 42°C.
• Heat-shock therapy: Recombinant DNA-infected cells are incubated on ice for a short period of time, after which they are briefly heated to 42°C and then returned to the ice.

6.: How are recombinant vectors made? Why is a single recombinant vector made with just one kind of restriction endonuclease necessary?

Ans. Vectors with recombinant DNA are created. At a specific restriction point, a restriction enzyme cuts the vector DNA. Using the enzyme ligase, the foreign DNA is combined with the vector DNA to form the recombinant vector.

At a specific sequence known as the recognition site, a restriction enzyme recognises and cleaves the DNA. In order to produce identical sticky ends in both DNA molecules to allow joining, the same restriction enzyme is utilised to cut the DNA segment from both the vector and the other source.

7. Incorporate “BAC” and “YAC”. What are they, and why do they serve the purposes that they do?

Ans. Bacterial artificial chromosome and yeast artificial chromosome are both abbreviations for artificial chromosomes. These are the DNA cloning vectors. DNA from the cell is extracted and reduced to relatively smaller sizes called fragments before being used for sequencing. In an appropriate host, DNA fragments are cloned using specialised vectors like BAC and YAC. Automated DNA sequences are then used to sequence DNA fragments.

8. How does the selectable marker function of the p-galactosidase coding sequence? Why is it preferred to antibiotic resistance genes as a selectable marker? Explain.

Chooseable marker: It facilitates the identification of transformants or their selection, the elimination of non-transformants, and the selective growth of the transformants.

By causing transformed cells to exhibit the property of insertional inactivation, ß-galactosidase functions as a selective marker. Recombinants and non-recombinants are distinguished in this procedure based on how much colour is produced when a chromogenic substrate is present. The enzyme ß-galactosidase is rendered inactive by the insertion of recombinant DNA into its coding region. As a result, bacterial colonies with plasmids implanted do not exhibit colouration, but those without plasmids do.

9. Give an explanation for the following statements. 

• DNA cannot cross a cell membrane into a host cell. 
• When DNA is isolated for genetic engineering, proteases are added. 
• In a vector, a single cloning site is recommended.

Ans

• Hydrophilic molecules cannot diffuse across the plasma membrane’s lipid bilayer, only hydrophobic molecules can. The sugar-phosphate backbone of DNA prevents it from passing through the cell membrane since it is hydrophilic.
• Proteins in the solution are broken down into their individual amino acids by proteases. The proteins might then interfere with any subsequent DNA treatment if they are not eliminated from the DNA preparation process (such as the action of restriction endonuclease, DNA ligase, etc).
• Single cloning sites are preferable since multiple recognition sites inside the vector would result in the generation of fragments, complicating the cloning of genes.

10. What function(s) do each of the following play in biotechnology? 

• Gel-electrophoresis
• Restriction endonuclease 
• pBR322’s selectable markers

Ans.

• The method known as gel-electrophoresis enables the separation and visualisation of DNA fragments on an agarose gel matrix. Since the DNA fragments are negatively charged molecules, an electric field causes them to split and travel in the direction of the anode (+ ve). Due to the gel’s sieving effect, DNA fragments are sorted according to their size.
• Endonucleases with restriction: These are the bacterial enzymes that recognise and bind to the particular nucleotide sequences, or “recognition sites,” on dsDNA to cut it into fragments. These enzymes are used to create DNA molecules that are recombinant and comprise DNA from many sources.
• In pBR322, selectable markers facilitate the selection and identification of transformants. Two antibiotic resistance genes, ampicillin and tetracycline, are included in pBR322, an E. coli cloning vector, and they serve as selectable markers. The recombinant plasmid in pBR322 loses tetracycline resistance when a foreign DNA is ligated at the site of the tetracycline resistance (tetR) gene because of the insertional inactivation of the foreign DNA, but it can still be distinguished from non-recombinants by growing the transformants on ampicillin-containing medium. The transformants that are developing on the medium containing ampicillin are subsequently transferred to the medium containing tetracycline. Recombinant organisms thrive on media containing ampicillin but not tetracycline, whereas non-recombinant organisms grow on both media.

11. Why were bacteria used to create a synthetic recombinant DNA molecule for the first time? Mention the scientists who did this and how they did it.

Ans.

• Because it was possible to combine an antibiotic-resistance gene with a native plasmid of the bacterium, Salmonella typhimurium was chosen as the first artificial recombinant DNA molecule. This was made possible by the accessibility of DNA ligase and restriction enzymes.
• By removing a section of DNA from a plasmid that was responsible for giving antibiotic resistance, Stanley Cohen and Herbert Boyer succeeded in isolating the antibiotic resistance gene in 1972. The development of restriction enzymes made it possible to cut DNA at particular locations. Using the DNA ligase enzyme, the cut DNA was joined to the plasmid DNA. The DNA linked to the plasmid serves as a vector to transfer.

12. State the origin of the DNA polymerase that is employed in PCR. Why is it used?

Ans. Taq polymerase, which is derived from Thermus aquaticus, is the DNA polymerase used in PCR. It is a thermostable enzyme that can resist high temperatures and is utilised in the phase that separates DNA strands after denaturation. As a result, it can be applied to numerous rounds of DNA amplification without losing its integrity.

13. Describe the functions of (i) high temperature, (ii) primers, and (iii) bacteria.

The polymerase chain reaction is carried out by Thermus aquaticus.

• Impact of heat: The DNA strands are split during PCR (in vitro) by heating at 95°C for two minutes. Heating causes the H-bonds between the bases of two strands to break, which causes the strands to unwind.
• Function of primer: To begin DNA polymerization in PCR, primers—short DNA segments of roughly 20 bp—are necessary. At a temperature of 40–50°C, the primers hybridise to their corresponding sequence on the DNA strands and aid in DNA polymerization.
• Thermus aquaticus’s function: Thermus aquaticus has been used to isolate an enzyme known as Taq polymerase. Because this bacteria can sustain temperatures of up to 95°C, the enzyme can also withstand high temperatures without becoming denatured. As a result, this enzyme is utilised in PCR rather than regular DNA polymerase.

Important Question for Class 12 Biology Chapter 11

Chapter 11 Biotechnology Principles and Its Processes Summary

The larger field of study and development known as “biotechnology” makes use of live creatures’ technology and applications to create goods that are beneficial to human well-being. Karoly Ereky is regarded as the founder of biotechnology since he originally used the word “biotechnology.”

Genetic engineering and bioprocess engineering are two of the basic concepts of contemporary biotechnology, according to this discipline. By altering the phenotypic of the target species, genetic engineering is utilised to edit their DNA. To enable the development of numerous desirable bacteria as well as other eukaryotic cells in large quantities, bioprocess engineering preserves the sterile environment which is employed in the creation of fresh or altered biotechnology items, such as vaccines, enzymes, and antibiotics.

Conclusion

Students may study and review the topics for 12th board exams and competitive examinations by looking through all the significant topics in Class 12 Biology Chapter 11. Additionally, it will aid in their comprehension of the basic concepts taught in the chapter Biotechnology Principles as Well as its Processes. These significant questions have been carefully constructed so that they address both conceptual and applicational aspects of the subject matter. Students may have a good understanding of the themes by consulting those questions and answers for the major issues in Biotechnology Principles as well as its Processes since the answers are comprehensive and provide a theoretical understanding.