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| Name of Board | AHSEC |
| Class: | Assam Board Class 12 |
| Subject: | AHSEC Class 12 Biology |
| Number of Chapter: | 09 |
| Chapter Name | Biotechnology: Principles Processes |
| Content Type: | Text, Images and PDF Format |
| Academic Year: | 2024-25 |
| Medium: | English |
| Available Solution Link: | AHSEC Class Biology Notes |
AHSEC Class 12th Biology Chapter: 9 BIOTECHNOLOGY: PRINCIPLES AND PROCESSES
[A] VERY SHORT ANSWER TYPE QUESTIONS: (1 MARK EACH)
1. What do you understand by PCR?
Ans: PCR stands for polymerase chain reaction in which multiple copies of the gene (or DNA) of interest is synthesised in vitro using two sets of primers and the enzyme DNA polymerase.
2. What is Biotechnology?
Ans: Biotechnology is integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services.
3. Define recombinant DNA technology. What is the popular terminology of it.
Ans: The technology which includes formation of recombinant DNA and introduction of recombinant DNA into an appropriate host is called recombinant DNA technology. It is popularly called genetic engineering.
4. What is chemical scalpe or molecular scissor and what is its function?
Ans: Molecular scissors are restriction enzymes. Its function is to cut DNA at specific locations.
5. What do you mean by bioreactors?
Ans: Bioreactors are vessels in which raw materials are biologically converted into specific products by microbes, plant and animal cells or their enzymes.
6. What is cloning vector?
Ans: Cloning vectors are carriers or vehicles of desired DNA fragments which can replicate independently to increase copies of desired genes in the host cell.
7. Expand the terms Ori and Eco RI.
Ans: Ori – Origin of replication.
Eco RI – Escherichia coli RY B.
8. What is gene gun?
Ans: Gene gun is a technique of bombarding microparticles of gold and tungsten coated with DNA with great velocity into the target cell.
9. What is the function of DNA ligase?
Ans: The function of DNA ligase is to join two individual fragments of double stranded DNA.
10. In respect to mode of action how can you differentiate enzyme exonuclease from endonuclease?
Ans: Exonucleases remove nucleotides from the ends of the DNA whereas endonucleases make cuts at specific positions within the DNA.
11. What is competent cell?
Ans. A cell that has the ability to pick up genes and plasmids from outside is called a competent cell.
12. Who first generated the recombinant Dna molecules?
Ans. Starby Cohen and Herbesrt Boyer.
13. What is gene cloning?
Ans. Gene cloning ins the formation of multiple identical coipes of any template DNA.
[B] FILL UP THE BLANKS : (1 MARK)
1. Each restriction endonuclease recognizes a specific- in the DNA.
Ans. Recognition sequence.
2. In plants recombinant DNA is injected into the nucleus by a method known as____
Ans. Gene gun
3. Ri and Ti plasmids are found in_____
Ans. Bacteria (Agrobacterium)
4. PCR stand for _____
Ans. Polymerase chain reaction
5. _____are known as molecular scissors.
Ans. Restriction enzymes
6. The first restriction endonuclease recognized is_____
Ans. Hind II
7. deals with large scale production and marketing of products and process using live organisms, cells or enzymes.
Ans. Downstream processing
8. Most commonly used bioreactors are of
Ans. Stirring type
9. A piece of DNA is introduced in a host bacterium through –
Ans. Vectors
10. Gel electrophoresis is used for.
Ans. Separation of DNA fragments
11. _______a crown gall bacterium is called natural ge- netic engineer of plants.
Ans. Agrobacterium tumifaciens
12. Genetic engineering is also known as________DNA technology.
Ans. recombinant
13. Large scale production of biotechnological products involve use of_______.
Ans. Bioreactors.
[C] SELECT THE TRUE AND FALSE STATEMENTS.
1. Bacteria protect their nucleoid from restriction endonuclease through methylation.
Ans. True
2. Transgenic plants are developed by introduction of foreign genes.
Ans. True
3. Function of restriction enzyme is to cut DNA at the ends.
Ans. False
4. DNA fragments are joined by enzyme polymerase.
Ans. False
5. Bacteria protect themselves from virus by fragmenting viral DNA with endonuclease.
Ans. False
6. Restriction enzymes are also known as molecular markers.
Ans. False
7. An antibiotic resistance gene in a vector usually helps in the selection of transformed cells.
Ans. False
8. The most common bacterium used in genetic engineering in Escherichia.
Ans. True
9. Hargovind Khurana was awarded the Noble Prize for the development of PCR technique.
Ans. False
10. Genetic engineering is a technique which involves deliberate manipulation of genes within or between the species.
Ans. True
11. Plasmids are circular extra chromosomal DNA in Bac- teria.
Ans.: True
12. DNA ligases are used to cleave a DNA molecule.
Ans.: False
13. Bacteria protect them from viruses by fragmenting viral DNA with endonucleae.
Ans.: True
[II] SHORT QUESTIONS : (2 MARKS)
1. What is DNA ligase?
Ans: DNA ligase are enzymes that form phosphodiester bonds between adjacent nucleotides and covalently link two individual fragments of double stranded DNA. They are also called ‘genetic gun’.
2. Define genetic engineering. Mention the tools used in genetic engineering.
Ans: Genetic engineering is the techniques to alter the chemistry of genetic material (DNA and RNA) to introduce these into host organisms and thus change the phenotype of the host organism.
The tools of genetic engineering are
(i) Restriction enzymes
(ii) Polymerase enzymes
(iii) Ligases
(iv) Vectors
(v) Host organisms
3. What is gene gun? Give its working principle.
Ans: Gene gun is a technique of bombarding microparticles of gold or tungsten coated with DNA with great velocity into the target cell.
It is a vectorless direct gene transfer in which the desired DNA is directly inserted into the plant cells with high velocity.
4. What are transgenic plants? Give examples.
Ans: The plants produced through genetic engineering contain genes usually from an unrelated organism, called transgenes and the plants having transgenes are called transgenic plants.
Examples:
(i) insect resistant plants like Bt cotton
(ii) Brassica napus which produces a protein hirudin.
(iii) ‘Flavr Savr’ tomato which prevent post harvest losses.
(iv) Vitamin A enriched golden rice.
5. How is DNA isolated in purified form from a bacterial cell?
Ans: DNA is isolated in purified form by treating the bacterial cells with the enzyme such as lysozyme to remove the cell wall. The RNA thus released can be removed by treating them with ribonuclease and enzyme proteases is added to remove proteins.” Finally chilled ethanol is added to precipitate the purified DNA.
6. Name the source organism from which Ti plasmid is isolated. Explain the use of this plasmid in biotechnology.
Ans: Ti plasmid is isolated from Agrobacterium tumefaciens.
The T-DNA transform normal plant cells into a tumour and direct these tumour cells to produce the chemical required by the pathogen. The Ti plasmid of Agrobacterium tumefaciens has now been modified into a cloning vector which is not pathogenic to the plant but is still able to use the mechanisms to deliver genes of our interest into a variety of plants.
7. Why is Agrobacterium mediated genetic transformation described as natural genetic engineering in plants?
Ans: Agrobacterium tumefaciens is a pathogen of several dicot plants which exhibit natural genetic engineering in plants because-
(i) It is able to deliver a piece of DNA called ‘T-DNA’ to transform normal plant cell into a tumour cell.
(ii) The DNA transforms the normal cells into tumour cells which direct them to produce the chemical essential for the pathogen.
8. What is recombinant DNA? How do enzymes restriction endonuclease and DNA ligase help its formation?
Ans: Recombinant DNA is the DNA formed by combining DNA from two different organisms.
Restriction endonuclease inspects the length of a DNA sequence and once it finds its specific recongition 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. This results in the formation of single stranded overhanging stretches at the end of each strand called sticky ends which can be joined together using DNA ligases.
9. Do eukaryotic cells have restriction endonuclease? Justify your answer.
Ans: No, cukaryotic cells do not have restriction endonucleases. It is present in prokaryotic cells like bacteria where they act as defence mechanism to restrict the growth of bacteriophages.
10. While doing a PCR, denaturation step is missed, what will be its effect on the process. Ans: If denaturation of double stranded DNA does not take place, then primers will not be able to anneal to the template, no extension will take place and hence no amplification will occur.
11. What are selectable markers? What is their use in genetic engineering?
Ans: Selectable markers are nucleotide sequences or genes which are antibiotic resistant.
It helps in identifying and eliminating non-transformants and will permit the growth of transformants only.
12. A recombinant DNA is found when sticky ends of vector DNA and foreign DNA join. Explain how the sticky ends are formed and get joined.
Ans: Restrictrion enzymes likes Eco RI cuts the vector DNA and foreign DNA or little away from the centre of the palindromic sites but between the same two bases on the opposite strands. This leaves single stranded overhanging stretches called sticky ends on each strand. They form hydrogen bonds with their complementary cut counterparts facilitated by the enzyme DNA ligase.
13. Why enzyme cellulose is used for isolating genetic material from plant cells but not animal cells?
Ans. Cellulose is present in the plant cell wall, so cellulose enzyme is added to the plant cell to digest cellulose, so that the genetic material can be isolated. But in animal cell cellulose in absent so cellulose enzyme is not added.
14. What are major steps involved in gene cloning tech- nique?
Ans. (i) Identification of DNA with deierable genes.
(ii) Introduction of the identified DNA into the host.
(iii) maintenance of introduced DNA in the host and transfer of the DNA to its progeny.
15. What are molecular scissors? Give at least two ex- amples of it.
Ans. Restriction enzymes are called molecular scissors as they cut DNA at specific locations.
Two examples are ECORI and Hind II.
[III] SHORT QUESTIONS: (3 MARKS)
1. Name the specific enzymes used to break the cells of organisms like bacteria, eukaryotic plant and fungus and release DNA along with their macromolecules.
Ans: Bacteria – lysozyme Eukaryotic plants – cellulase Fungi Chitinase
2. What is downstream processing in respect of biotechnology?
Ans: All the processes to which a product is subjected to before being marketed as a finished product is called downstream processing. It includes
(a) Separation of the product from the reactor.
(b) Purification of the product.
(c) Formulation of the product with suitable preservatives.
(d) Quality control testing and clinical trials in case of drugs.
3. State the basic steps involved in genetically modifying an organism.
Ans: The steps are
(i) identification of DNA with desirable genes.
(ii) introduction of the identified DNA into the host.
(iii) maintenance of introduced DNA in the host and transfer of the DNA to its progeny.
4. Explain any three methods to force ‘alien’ or recombinant DNA into host cells.
Ans: (i) Micro-injection method: Here recombinant DNA is directly injected into the nucleus of an animal cell.
(ii) Gene gun: Cells are bombarded with high velocity micro particles of gold or tungsten coated with DNA in plants.
(iii) Disarmed pathogen vectors: When allowed to infect the cell, transfer the recombinant DNA into the host.
5. State the principle underlying ‘gel electrophoresis’ and mention two applications of this technique in Biotechnology.
Ans: The principle underlying gel electrophoresis is that, DNA fragments are negatively charged so they are moved to anode under an electric field through a medium or matrix. This matrix gel acts as sieve and DNA fragments resolve according to their size.
Two applications are
(i) The DNA fragments are used in constructing recombinant DNA by joining them with cloning vectors.
(ii) DNA fragments are also used for DNA fingerprinting.
6. Write the major steps involved in gene cloning.
Ans: The major steps involved in gene cloning are-
(i) isolation of DNA.
(ii) fragmentation of DNA by restriction endonucleases.
(iii) isolation of a desired DNA fragment.
(iv) ligation of the DNA fragment into a vector. (v) transferring the recombinant DNA into the host.
(vi) culturing the host cells in a medium at large scale.
(vii) Extraction of the desired product.
7. What is meant by recognition sequence? Write the recognition site of EcoRI and where it cuts the DNA.
Ans: Recognition sequence is the specific base sequence of DNA where the restriction enzyme cuts the DNA.
The recognition site of EcoRI is
5′ GAATTC – 3′
3′- CTTAAG – 5′
EcoRI cuts the DNA between bases G and A only when the sequence GAATTC is present in the DNA.
8. Distinguish between –
(i) Plasmid DNA and Chromosomal DNA
Ans:
Plasmid DNA
1. This is present in prokaryotic (bacterial) cells.
2. It is linear and associated with histone proteins.
3.It gives the cell extra characters like antibiotic resistance
Chromosomal DNA
1. This is present in eukaryotic cells.
2. This is the circular extra chromosomal DNA not associated with histone proteins.
3. It does not provide extra characters to the cell
(ii) Exonuclease and Endonuclease
Ans:
Exonuclease
1. These remove nucleotides from the ends of the DNA.
2. These act an single strand of DNA.
Endonuclease
1. These cut at specific regions within the DNA.
2. These act on both strands of DNA.
10. Give reasons of recombinant DNA formation from two sources of DNA.
Ans: (i) Recombinant DNA formation needs two sources so that one can act as vector DNA and the other as foreign DNA carrying gene of interest.
(ii) The alien DNA contains the desirable set of genes so the undesirable genes can be eliminated.
(iii) The alien piece of DNA when gets integrated into the genome of the recipient it will replicate and produce multiple copies of the desired gene.
11. What is Biotechnology? Discuss the principles of bio- technology.
Ans.: Biotechnology is the integration of natural science and organisms, cells, parts thereof and molecular analogues for products and services.
The principle of biotechnology are-
1. Genetic engineering: Techniques to alter the chemistry of genetic material (DNA and RNA), to introduce these into host organisms and thus change the phenotype of the host organism.
2. Chemical engineering: Maintenance of sterile ambience to enable growth of only the desired microbe leukaryotic cell the large quantities for the manufacture of biotechnological products like an- tibiotics, vaccines, enzymes etc.
12. Expand the term PCR. Write the principle of PCR.
Ans. PCR means polymerase chain reaction.
In PCR multiple copies of the gene of synthesised in vitro using two sets of primers (small chemically synthesised, oligonucleotide that are complementary to the regions of DNA) and the enzyme DNA polymerase. The enzyme extend the primers using the nucle- otides provided in the reaction and the genomic DNA as template. If the process of replication of DNA is repeated many time, the segment of DNA can be amplified to approximately billion times, i.e., 1 billion copies are made. Such repeated amplification is achieved by the use of a thermostable DNA polymerase (isolated from bacteria, thermus aquatious), which remain active during the high temperature induced denaturation of double stranded DNA.
13. Explain the process by which a bacterial cell can be made ‘competent’ in recombinant DNA technology.
Ans. Bacterial cell can be made competent by treating them with a specific concentration of a divalent cation. Such as calcium, which increases the efficiency with which DNA enters the bacte- rium through pores in its cell wall. Recombinant DNA can then be forced into such cell by incubating the cell 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.
(IV) LONG QUESTIONS : (5 MARKS)
1. EcoRI is used to cut a segment of foreign DNA to form a recombinant DNA. Show with the help of a diagram.
Ans:
(Steps in formation of recombinant DNA by action of restriction endonuclease enzyme EcoRi)
2. What is polymerase chain reaction and how can it be utilized for gene amplification.
Ans: Polymerase chain reaction is a technique in which multiple copies of the gene of interest is synthesised in vitro using two sets of primers and the enzyme DNA polymerase.
It involves the following steps for gene amplification
(i) Denaturation In this step the target DNA is heated to a high temperature, usually 94 to 96°C resulting in the separation of the two strands. Each single strand of the target DNA acts as a template for DNA synthesis.
(ii) Annealing: In this step the two oligo nucleotide primers anneal to each of the single stranded template DNA since the sequence of the primers is complementary to the 3′ end of the template DNA. This step is carried out at a lower temperature (usually 40°C to 60°C)
(iii) Extension: In this step deoxynucleoside) triphosphates,
Mg2+ and Taq polymerase synthesises the DNA strands complementary to template strand and leads to extension. The optimum temperature required for this step is 72°C.
Each cycle doubles the amount of DNA present previous to the cycle and helps in amplification of the gene of interest
3. Any recombinant DNA with a desired gene is required in billion copies for commercial use. How is the amplification done? Explain.
Ans: The process you’re describing is typically achieved through a technique called polymerase chain reaction (PCR). PCR is a method used to amplify a specific segment of DNA, making billions of copies of it within a short period of time. Here’s how it works:
1. Denaturation: The first step involves heating the DNA sample to a high temperature (usually around 94-98°C). This causes the double-stranded DNA to separate into two single strands, breaking the hydrogen bonds between the base pairs. This creates two template strands for the next step.
2. Annealing: The temperature is lowered to around 50-65°C. At this temperature, short DNA sequences called primers (which are designed to be complementary to sequences flanking the target DNA region) bind to the single-stranded DNA templates. These primers serve as starting points for DNA synthesis.
3. Extension: The temperature is raised slightly to around 72°C. DNA polymerase, an enzyme that catalyzes the synthesis of new DNA strands, adds nucleotides to the primers, extending them along the template strands. This process continues, creating new strands of DNA complementary to the original template strands.
By repeating these three steps, each cycle of PCR doubles the amount of DNA, resulting in exponential amplification. After a certain number of cycles (typically 20-40), billions of copies of the target DNA sequence are generated.
PCR is a crucial tool in molecular biology and genetics, used for various applications such as DNA sequencing, gene cloning, and genetic testing. Its ability to amplify specific DNA sequences quickly and efficiently has revolutionized many areas of research and technology.
4. Discuss the conceptual development of the principles of genetic engineering.
Ans: In traditional hybridisation experiments used in plant and animal breeding, hybrids come to have both desired and undesired genes. The undesired genes are very difficult to remove. Even the desirable genes are at times elusive. This drawback has been overcome by recombinant DNA technology.
Simple introduction of an alien gene into a cell is of no consequence, unless it replicates. Replication is possible if an alien gene becomes part of chromosome or extrachromasomol, DNA which has its origin of replication. Cohen and Boyer were the first to produce a recombinant DNA by attaching an antibiotic resistance gene to the plasmid of Salmonella typhimurium. This was carried out with the help of first restriction enzymes which cut the DNA at a particular regions having complementary sticky ends. The two DNAs were then joined with the aid of DNA ligase. The modified plasmid was then transferred into E.coli, a bacterium related to Salmonella. It could replicate there using DNA polymerase and nucleotides of the host and form multiple copies. Formation of multiple copies of a particular gene is called cloning. And the organism having a new gene is called genetically modified organism.
5. What are molecular scissors? Explain this role in the process of recombinant DNA technology.
Ans: The restriction endonucleases are called molecular scissors as they cut the DNA segments at particular locations.
The restriction endonuclease function 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 sequences in the DNA. The restriction enzymes cut the DNA strands a little away from the centre of the palindromic sites, but between the same two bases on the opposite strands. This leaves single stranded portions with overhanging stretches called sticky ends on each strand as they form hydrogen bonds with their complementary cut counterparts. This stickiness at the ends facilitates the action of the enzyme DNA ligase.
6. What is recombinant DNA technology? Wite a brief account of the process of recombinant DNA technology.
Ans. The technique in which desirable genes are isolated, cloned and transferred is called recombinant DNA technology.
Processes of r DNA Technology.
(i) Isolation of the Genetic Material: In order to cut the DNA with restriction enzymes, it needs to be in pure form. This can be achieved by treating bacterial cell with lysozyme, plant cells with cellulase and fungal cell with chitinase. To make free from RNA, proteins, polysaccharides, lipids the DNA is treated with ribonu- clease, protease, lipase etc. After removing macromolecules., DNA precipitates out by adding chilled ethanol.
(ii) Cutting of DNA at specific locations: The DNA is cut using restriction enzyme. The purified DNA is incubated with the specific restriction enzyme at conditions optimum for the enzyme to act. Agarose gel electrophoresis is employed to check the progres- sion of a restriction enzyme digestion.
(iii) Amplification of gene of interest using PCR: Poly- merase chain reaction is a reaction in which amplification of spe- cific DNA sequences is carried out in vitro.
(iv) Insertion of recombinant DNA into the host cell: Recipient cells after making them competent to receive, take up the rDNA in its surroundings that has been selected by the selectable markers.
(v) Obtaining the foreign gene product: Foreign gene when integrated with host cell multiplies and its products are obtained on large scale in bioreactors. Products obtained from bioreactors are then separated and purified. This is known as dowustream process- ing. The quality control testing is done by clinical trial.
7. What is bioreactor? Draw a labelled diagram of a sparged strred bioreactor and explain its functioning.
Ans. Breactors are vessels of large volumes (100-1000 litres) in which raw materials are biologically converted into specific prod- ucts.
Sparged stirred bioreactors: A sparged stirred tank reactor is usually cylindrical. The stirrer facilitates even mixing and oxygen availability throughout the bioreactor. The bioreactor also has an agitator system, on oxygen delivery system which is necessary for the cells that function better under aerobic conditions and a form control system. There is also temperature control and pH control system and sampling ports so that small volumes of the culture can be withdrawn periodically to know the growth of cells and concen- tration of extractable product.
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Last Words on AHSEC Class 12 Biology Chapter: 9 Biotechnology: Principles Processes
The Chapter 9 of AHSEC Class 12 Biology deals with Biotechnology: Principles Processes for a brief understanding. You can Download this HS 2nd Year Biology Notes in PDF 2025.
