Maharashtra Board Class 12 Biology Chapter 12 Exercise Biotechnology Solutions

Biotechnology Class 12 Exercise Question Answers Solutions Maharashtra Board

Class 12 Biology Chapter 12 Exercise Solutions Maharashtra Board

Biology Class 12 Chapter 12 Exercise Solutions

1. Multiple Choice Questions

Question 1.The bacterium which causes a plant disease called crown gall is
(a) Helicobacter pylori
(b) Agrobacterium tumifaciens
(c) Thermophilus aquaticus
(d) Bacillus thuringienesis
Answer: (b) Agrobacterium tumtfaciens
In simple words: Agrobacterium tumefaciens is a common soil bacterium that causes crown gall disease in plants by transferring a part of its DNA to the plant's genome.

🎯 Exam Tip: Remember the specific name of the bacterium and the disease it causes, as it's a fundamental concept in plant biotechnology.

Question 2.The enzyme nuclease hydrolyses - of polynucleotide chain of DNA.
(a) hydrogen bonds
(b) phosphodiester bonds
(c) glycosidic bonds
(d) peptide bonds
Answer: (b) phosphodiester bonds
In simple words: Nuclease enzymes specifically break the phosphodiester bonds that link nucleotides together in a DNA or RNA strand, thereby cutting the nucleic acid.

🎯 Exam Tip: Understand the specific type of bond that nucleases target in nucleic acids, as this is crucial to their function in genetic engineering.

Question 3.In vitro amplification of DNA or RNA segment is known as -
(a) chromatography
(b) southern blotting
(c) polymerase chain reaction
(d) gel electrophoresis
Answer: (c) polymerase chain reaction
In simple words: Polymerase Chain Reaction (PCR) is a laboratory technique used to rapidly make millions to billions of copies of a specific DNA segment, amplifying it from a very small sample.

🎯 Exam Tip: PCR is a cornerstone technique in molecular biology; know its full name and its primary application of amplifying nucleic acid segments.

Question 4.Which of the following is the correct recognition sequence of restriction enzyme hind III.
(a) 5′ -A-A-G-C-T-T- 3′
3' -T-T-C-G-A-A-5′
(b) 5′ - G-A-A-T-T-C-3′
3' - C-T-T-A-A-G-5'
(c) 5′ - C-G-A-T-T-C-3′
3' - G-C-T-A-A-G-5′
(d) 5′ - G-G-C-C-3′
3' - C-C-G-G-5'
Answer: (a) 5′ -A-A-G-C-T-T-3′
3′ -T-T-C-G-A-A-5′
In simple words: HindIII recognizes a specific palindromic sequence on DNA, which is a sequence that reads the same forwards on one strand and backwards on the complementary strand.

🎯 Exam Tip: Familiarize yourself with common restriction enzyme recognition sites, especially their palindromic nature and how they are read from 5' to 3' on complementary strands.

Question 5.Recombinant protein - is used to dissolve blood clots present in the body.
(a) insulin
(b) tissue plasminogen activator
(c) relaxin
(d) erythropoietin
Answer: (b) tissue plasminogen activator
In simple words: Tissue plasminogen activator (tPA) is a protein that helps dissolve blood clots by converting plasminogen into plasmin, an enzyme that breaks down fibrin.

🎯 Exam Tip: Know the therapeutic uses of key recombinant proteins; tPA is important for its role in treating conditions like heart attacks and strokes.

Question 6.Recognition sequence of restriction enzymes are generally - nucleotide long.
(a) 2 to 4
(b) 4 to 8
(c) 8 to 10
(d) 14 to 18
Answer: (b) 4 to 8
In simple words: Restriction enzymes typically recognize and cut DNA at short, specific sequences, which are usually 4 to 8 base pairs in length.

🎯 Exam Tip: The length of restriction enzyme recognition sequences is a basic characteristic; remember the typical range for these sites.

2. Very Short Answer Questions

Question 1.Name the vector which is used in production of human insulin through recombinant DNA technology.
Answer: PBR 322
In simple words: pBR322 is a common plasmid vector frequently used in recombinant DNA technology for cloning and expression of genes, including the production of human insulin.

🎯 Exam Tip: Knowing specific examples of vectors like pBR322 for particular applications such as insulin production is important for recall.

Question 2.Which cells from Langerhans of pancreas do produce a peptide hormone insulin?
Answer: cells of islets of Langerhans of a peptide hormone insulin.
In simple words: The beta cells located within the islets of Langerhans in the pancreas are responsible for producing the peptide hormone, insulin.

🎯 Exam Tip: Accurately identify the specific cells and their location responsible for insulin production, a key concept in endocrinology and biology.

Question 3.Give the role of Ca++ ions in the transfer of recombinant vector into bacterial host cell.
Answer: Ca++ ions promotes binding of plasmid DNA to lipo polysaccharides on bacterial cell surface. Then plasmid can enter the cell on heat shock.
In simple words: Calcium ions make bacterial cell membranes more permeable, allowing plasmid DNA to bind to lipopolysaccharides and facilitating its uptake into the cell, especially when followed by a heat shock.

🎯 Exam Tip: Understand the mechanism by which divalent cations like Ca++ enhance the competency of bacterial cells for DNA transformation, including the role of heat shock.

Question 4.Expand the following acronyms which are used in the held of biotechnology:
1. YAC
2. RE
3. dNTP
4. PCR
5. GMO
6. MAC
7. CCMB.
Answer:
1. YAC : Yeast Artificial chromosome
2. RE : Restriction Endonuclease
3. dNTP : Deoxyribonucleoside triphosphates
4. PCR : Polymerase Chain Reaction
5. GMO : Genetically Modified Organisms
In simple words: These acronyms represent fundamental terms and tools in biotechnology, ranging from DNA amplification and genetic modification to chromosomal vectors and research centers.

🎯 Exam Tip: Thoroughly learn the full forms of these common abbreviations, as they are frequently used in biotechnology and genetic engineering contexts.

6. MAC: Mammalian Artificial Chromosome
7. CCMB : Centre for Cellular and Molecular Biology

Question 5.Fill in the blanks and complete the chart.

🎯 Exam Tip: Be able to identify common GMOs and their respective beneficial applications, as this showcases an understanding of applied biotechnology.

3. Short Answer Type Questions

Question 1.Explain the properties of a good or ideal cloning vector for r-DNA technology.
Answer: Desired characteristics of ideal cloning vector are as follows:
1. Vector should be able to replicate independenly (through ori gene), so that as vector replicates, multiple copies of the DNA insert are also produced.
2. It should be able to easily transferred into host cells.
3. It should have suitable control elements like promoter, operator, ribosomal binding sites, etc.
4. It should have marker genes for antibiotic resistance and restriction enzyme recognition sites within them.
In simple words: An ideal cloning vector must be able to self-replicate, easily transfer DNA into host cells, contain necessary control elements for gene expression, and have selectable marker genes along with restriction sites for easy manipulation.

🎯 Exam Tip: Focus on the four core characteristics: origin of replication (ori), selectable marker, cloning sites, and ability to transfer, as these are critical for vector functionality.

Question 2.A PCR machine can rise temperature up to 100 °C but after that it is not able to lower the temperature below 70 °C automatically. Which step of PCR will be hampered first in this faulty machine? Explain why?
Answer:
1. If the faulty machine is not able to lower the temperature below 70 °C, then the primer annealing step will be hampered first.
2. Each primer has a specific annealing temperature, depending upon its A, T, G, C content.
3. For most of the primers annealing temperature is about 40-60 °C.
4. Hence, if temperature is more than primers annealing temperature, it will be able to pair with its complementary sequence in ssDNA.
In simple words: The annealing step of PCR would be most affected because primers require lower temperatures (typically 40-60 °C) to bind to their complementary DNA sequences, and a faulty machine stuck above 70 °C would prevent this binding.

🎯 Exam Tip: Understanding the temperature requirements for each PCR step (denaturation, annealing, extension) is vital; especially note the low temperature needed for primer annealing.

Question 3.In the process of r-DNA technology, if two separate restriction enzymes are used to cut vector and donor DNA then which problem will arise in the formation of r-DNA or chimeric DNA? Explain.
Answer: In the process of r-DNA technology, if two separate restriction enzymes are used to cut vector and donor DNA, then it will result in fragments with different sticky ends which will not be complementary to each other.
In simple words: Using different restriction enzymes to cut the vector and donor DNA would create incompatible sticky ends, preventing them from ligating together to form recombinant DNA.

🎯 Exam Tip: Emphasize the requirement for using the *same* restriction enzyme (or enzymes that produce compatible sticky ends) on both vector and insert DNA to ensure successful ligation.

Question 4.

🎯 Exam Tip: Create a mental map of various recombinant proteins and their primary medical applications; this demonstrates a practical understanding of biotechnology's impact.

4. Long Answer Type Questions

Question 1.(i) Define and explain the terms Bioethics.
Answer:
1. Bioethics is the study of moral vision, decision and policies of human behaviour in relation to biological phenomena or events.
2. Bioethics deals with wide range of reactions on new developments like cloning, transgenic, gene therapy, eugenics, r-DNA technology, in vitro fertilization, sperm bank, gene therapy, euthanasia, death, maintaining those who are in comatose state, prenatal genetic selection, etc.
3. Bioethics also includes the discussion on subjects like what should and should not be done in using recombinant DNA techniques.
Ethical aspects pertaining to the use of biotechnology are:
1. Use of animals cause great sufferings to them.
2. Violation of integration of species caused due to transgenosis.
3. Transfer of human genes into animals and vice versa.
4. Indiscriminate use of biotechnology pose risk to the environment, health and biodiversity.
5. The effects of GMO on non-target organisms, insect resistance crops, gene flow, the loss of diversity.
6. Modification process disrupting the natural process of biological entities.
In simple words: Bioethics examines the moral implications and societal impact of biological discoveries and biotechnological applications, guiding decisions on what is ethically permissible in areas like genetic engineering, cloning, and medical treatments.

🎯 Exam Tip: Define bioethics clearly and provide a range of examples for both biotechnological advancements and the ethical concerns they raise to show a comprehensive understanding.

(ii) Define and explain the term Biopiracy.
Answer:
1. Biopiracy is defined as 'theft of various natural products and then selling them by getting patent without giving any benefits or compensation back to the host country'.
2. It is unauthorized misappropriation of any biological resource and traditional knowledge.
3. It is bio-patenting of bio-resource or traditional knowledge of another nation without proper permission of the concerned nation or unlawful exploitation and use of bioresources without giving compensation.
Following are the examples of biopiracy:
(a) Patenting of Neem (Azadirachta indica):
1. Pirating India's traditional knowledge about the properties and uses of neem, the USDA and an American MNC W.R. Grace sought a patent from the European Patent Office (EPO) on the "method for controlling on plants by the aid of hydrophobic extracted neem oil,” in the early 90s.
2. The patenting of the fungicidal properties of Neem, was an example of biopiracy.
(b) Patenting of Basmati:
1. Texmati is a trade name of "Basmati rice line and grains" for which Texas based American company Rice Tec Inc was awarded a patent by the US Patent and Trademark Office (USPTO) in 1997.
2. This is a case of biopiracy as Basmati is a long-grained, aromatic variety of rice indigenous to the Indian subcontinent.
3. Very broad claims about “Inventing” the said rice was the basis of patent application.
4. The UPSTO has rejected all the claims due to people movement against Rice Tec in March 2001.
(c) Haldi (Turmeric) Biopiracy:
1. A patent claim about the healing properties of Haldi was made by two American researchers of Indian origin of the University of Mississippi Medical Center, to the US Patent and Trademark Office.
2. They were granted a patent in March 1995.
3. This is an example of biopiracy because healing properties of Haldi is not a new discovery, but it is a traditional knowledge in ayurvedas for centuries.
4. The Council of Scientific and Industrial Research (CSIR) applied to the US Patent Office for a reexamination and they realized the mistake and cancelled the patent.
In simple words: Biopiracy is the unethical and unauthorized appropriation of genetic resources or traditional knowledge from indigenous communities or nations, often for commercial gain, without fair compensation or permission.

🎯 Exam Tip: Define biopiracy clearly and support your definition with specific, well-known examples like the patenting disputes over Neem, Basmati, and Turmeric to illustrate its impact.

(iii) Define and explain the term Biopatent.
Answer:
1. Biopatent is a biological patent awarded for strains of microorganisms, cell lines, genetically modified strains, DNA sequences, biotechnological processes, product processes, product and product applications.
2. It allows the patent holder to exclude others from making, using, selling or importing protected invention for a limited period of time.
3. Duration of biopatentis five years from the date of the grant or seven years from the date of filing the patent application, whichever is less.
4. Awarding biopatents provides encouragement to innovations and promote development of scientific culture in society. It also emphasizes the role of biology in shaping human society.
5. First biopatent was awarded for genetically engineered bacterium 'Pseudomonas' used for clearing oils spills.
6. Patent jointly issued by Delta and Pineland company and US department of agriculture having title 'control of plant gene expression', is based on a gene that produces a protein toxic to plant and thus prevents seed germination.
This patent was not granted by Indian government. Such a patent is considered morally unacceptable and fundamentally unequitable. Such patents would pose a threat to global food security as financially powerful corporations would acquire monopoly over biotechnological process.
In simple words: A biopatent grants exclusive rights to an inventor for a biological entity or process, such as a microorganism, DNA sequence, or biotechnological method, for a specific period, encouraging innovation but also raising ethical concerns about access and equity.

🎯 Exam Tip: Explain the purpose and scope of biopatents, including their duration and examples, and discuss the dual nature of their benefits (innovation) and ethical challenges (monopoly, access).

Question 2.Explain the steps in process of r-DNA technology with suitable diagrams.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र रीकॉम्बिनेंट डीएनए (rDNA) तकनीक की प्रक्रिया को दर्शाता है। इसमें एक डोनर कोशिका से वांछित डीएनए को अलग करना, उसे प्रतिबंध एंजाइमों द्वारा काटना, और फिर इस कटे हुए डीएनए खंड को एक वेक्टर (जैसे प्लाज्मिड) में जोड़ना शामिल है। यह rDNA फिर एक जीवाणु होस्ट कोशिका में डाला जाता है, जो गुणा करता है और वांछित प्रोटीन का उत्पादन करता है।
Answer: The steps involved in gene cloning are as follows:
(1) Isolation of DNA (gene) from the donor organism:
- To obtain the desired gene to be cloned, the cells of the donor organism are sheared with the blender and treated with suitable detergent. Genetic material is then isolated and purified.
- Isolated purified DNA is then cleaved using restriction Endonucleases.
- Restriction fragment containing desired gene is isolated and selected for cloning. This is now called foreign DNA or passanger DNA.
- A desired gene can also be obtained directly from genomic library or c-DNA library.
(2) Insertion of desired foreign gene into a cloning vector (vehicle DNA):
- The foreign DNA or passanger DNA is inserted into a cloning vector (vehicle DNA) like bacterial plasmids and the bacteriophages like lamda phage and M13. The most commonly used plasmid is pBR 322.
- Plasmids are isolated from the bacteria and are cleaved by using same RE which is used in the isolation of the desired gene from the donor.
- Enzyme DNA ligase is used to join foreign DNA and the plasmid DNA.
- Plasmid DNA containing foreign DNA is called recombinant DNA (r-DNA) or chimeric DNA.
(3) Transfer of r-DNA into suitable competent host or cloning organism:
- The r-DNA is introduced into a competent host cell, which is mostly a bacterium.
- Host cell takes up naked r-DNA by process of 'transformation' and incorporates it into its own chromosomal DNA which finally expresses the trait controlled by passenger DNA.
- The transfer of r-DNA into a bacterial cell is assisted by divalent Ca++.
- The cloning organisms are E.coli and Agrobacterium tumifaciens.
- The competent host cells which have taken up r-DNA are called transformed cells.
- By using techniques like electroporation, microinjection, lipofection, shot gun, ultrasonification, biolistic method, etc. Foreign DNA can also be transferred directly into the naked cell or protoplast of the competent host cell, without using vector.
- In plant biotechnology the transformation is through Ti plasmids of A. tumifaciens.
(4) Selection of the transformed host cell:
- For isolation of recombinant cell from non-recombinant cell, marker gene of plasmid vector is employed.
- For example, pBR322 plasmid vector contains different marker genes like ampicillin resistant gene and tetracycline resistant gene. When pstl RE is used, it knocks out ampicillin resistant gene from the plasmid, so that the recombinant cells become sensitive to ampicillin.
(5) Multiplication of transformed host cell:
- The transformed host cells are introduced into fresh culture media where they divide.
- The recombinant DNA carried by them also multiplies.
(6) Expression of gene to obtain desired product. Then desired products like enzymes, antibiotiocs etc. separated and purified through down stream processing using bioreactors.
In simple words: Recombinant DNA technology involves isolating a gene, cutting it with restriction enzymes, inserting it into a vector, introducing the vector into a host cell, selecting transformed cells, multiplying them, and finally expressing the gene to produce a desired product.

🎯 Exam Tip: Clearly delineate each step of r-DNA technology from gene isolation to product expression, emphasizing the role of key enzymes and vectors, and ensure the diagram accurately reflects these stages.

Question 3.Explain the gene therapy. Give two types of it.
Answer: Gene therapy is the treatment of genetic disorders by replacing, altering or supplementing a gene that is absent or abnormal and whose absence or abnormality is responsible for the disease.
Types of gene therapy:
(a) Germ line gene therapy:
1. In this germ cells are modified genetically to correct a genetic defect.
2. Normal gene is introduced into germ cells like sperms, eggs, early embryos.
3. It allows transmission of the modified genetic information to the next generation.
4. Although it is highly effective in treatment of the genetic disorders, its use is not preferred in human beings because of various technical and ethical reasons.
(b) Somatic cell gene therapy:
1. In this somatic cells are modified genetically to correct a genetic defect.
2. Healthy genes are introduced in somatic cells like bone marrow cells, hepatic cells, fibroblasts endothelium and pulmonary epithelial cells, central nervous system, endocrine cells and smooth muscle cells of blood vessel walls.
3. Modification of somatic cells only affects the person being treated and the modified chromosomes cannot be passed on the future generations.
4. Somatic cell gene therapy is the only feasible option and the clinical trials have already employed for the treatment of disorders like cancer, rheumatoid arthritis, SCID, Gaucher's disease, familial hypercholesterolemia, haemophilia, phenylketonuria, cystic fibrosis, sickle-cell anaemia, Duchenne muscular dystrophy, emphysema, thalassemia, etc.
In simple words: Gene therapy aims to treat genetic disorders by correcting or replacing faulty genes, primarily through two types: germ line therapy, which alters reproductive cells and is heritable, and somatic cell therapy, which targets body cells and affects only the treated individual.

🎯 Exam Tip: Define gene therapy and differentiate clearly between germ line and somatic cell gene therapy, outlining their mechanisms, ethical considerations, and clinical applications/limitations.

Question 4.How are the transgenic mice used in cancer research?
Answer:
1. Transgenic mice are used in various research areas of cancer research.
2. Transgenic mice containing a particular oncogene (cancer causing gene) develop specific cancer.
3. They are used to study the relationship between oncogenes and cancer development, cancer treatment and prevention of malignancy.
4. The transgenic mouse model for the investigation of the breast cancer was developed in the laboratory of Philip Leder in Harvard (USA).
5. Transgenic mice containing oncogenes myc and ras were analyzed to find out role of these genes in the development of breast cancer.
In simple words: Transgenic mice engineered to carry specific oncogenes are crucial models in cancer research, allowing scientists to study tumor development, test new therapies, and understand the roles of particular genes in various cancers.

🎯 Exam Tip: Explain how genetically modified mice serve as invaluable models in cancer research by mimicking human disease progression and enabling the study of oncogenes and therapeutic interventions.

Question 5.Give the steps in PCR or polymerase chain reaction with suitable diagrams.
ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र पॉलीमरेज़ चेन रिएक्शन (PCR) के चरणों को दर्शाता है। इसमें डीएनए के एक वांछित खंड की अनेक प्रतियां बनाने के लिए तापमान में बार-बार बदलाव का उपयोग किया जाता है। मुख्य चरणों में डीएनए का विनेचुरेशन (अलग करना), प्राइमर का एनीलिंग (जुड़ना) और डीएनए पोलीमरेज़ द्वारा नए डीएनए स्ट्रैंड्स का विस्तार शामिल है, जिसके परिणामस्वरूप प्रत्येक चक्र में डीएनए की प्रतियों की संख्या दोगुनी हो जाती है।
Answer:
(1) The DNA segment and excess of two primer molecules, four types of dNTPs, the thermostable DNA polymerase are mixed together in 'eppendorf tube'.
(2) One PCR cycle is of 3-4 minutes duration and it involves following steps:
- Denaturation : The reaction mixture is heated at 90-98°C. Due to this hydrogen bonds in the DNA break and two strands of DNA separate. This is called denaturation.
- Annealing of primer: When the reaction mixture is cooled to 40-60°C, the primer pairs with its complementary sequences in ssDNA. This is called annealing.
- Extension of primer : In this step, the temperature is increased to 70-75°C. At this temperature thermostable Taq DNA polymerase adds nucleotides to 3'end of primer using single-stranded DNA as template. This is called primer extension. Duration of this step is about two minutes.
(3) In an automatic thermal cycler, the above three steps are automatically repeated 20-30 times.
(4) Thus, at the end of 'n' cycles 2n copies of DNA segments, get synthesized.
In simple words: PCR amplifies DNA through repetitive cycles of three temperature-dependent steps: denaturation separates DNA strands, annealing allows primers to bind, and extension synthesizes new DNA strands, resulting in exponential DNA copy production.

🎯 Exam Tip: Explain each of the three PCR steps (denaturation, annealing, extension) with their respective temperature ranges and what happens at each stage, alongside a clear, labeled diagram.

Question 6. What is a vaccine? Give advantages of oral vaccines or edible vaccines.
Answer:
1. A vaccine is a biological preparation that provides active acquired immunity against a certain disease.
2. Vaccine is often made from a weakened or killed form of the microorganism, its toxins or one of its surface protein antigens.
3. Edible vaccine is an edible plant part engineered to produce an immunogenic protein, which when consumed gets recognized by immune system.
4. Immunogenic protein of certain pathogens are active when'administered orally.
5. When animals or mainly humans consume these plant parts, they get vaccinated against certain pathogen.
6. Oral or edible vaccines have low cost, they are easy to administer and store.
In simple words: A vaccine is a biological agent that boosts immunity against a disease. Edible vaccines, produced in plants, offer a cost-effective and easy-to-administer way to provide immunity by consuming plant parts engineered to produce immunogenic proteins.

🎯 Exam Tip: Focus on the definition of a vaccine and the specific benefits of oral/edible vaccines, such as cost-effectiveness and ease of administration and storage, as these are common evaluation points.

Question 7. Enlist different types of restriction enzymes commonly used in r-DNA technology? Write on their role.
Answer:
1. Different restriction enzymes commonly used in r-DNA technology are Alu I, Bam HI, Eco RI, Hind II, Hind III, Pst I, Sal I, Taq I, Mbo II, Hpa I, Bgl I, Not I, Kpn I, etc.
2. They are the molecular scissors which recognize and cut the phosphodiester back bone of DNA on both strands, at highly specific sequences.
3. The sites recognized by them are called recognition sequences or recognition sites.
4. Different restriction enzymes found in different organisms recognize different nucleotide sequences and therefore cut DNA at different sites.
5. Restriction cutting may result in DNA fragments with blunt ends or cohesive or sticky ends or staggered ends (having short, single stranded projections).
6. Restriction endonucleases like Bam Hl and EcoRI produce fragments with sticky ends.
7. Restriction endonucleases like Alu I, Hind III produce fragments with blunt ends.
8. Type I restriction endonucleases fuction simultaneously as endonuclease and methylase e.g. EcoK.
9. Type II restriction endonucleases have separate cleaving and methylation activities. They are more stable and are used in r-DNA technology e.g. EcoRI, Bgll. They cut DNA at specific sites within the palindrome.
10. Type III restriction endonucleases cut DNA at specific non-palindromic sequences e.g. Hpal, Mboll.
11. In bacterial cells, REs destroy various viral DNAs that might enter the cell, thus restricting the potential growth of the virus.
In simple words: Restriction enzymes are like molecular scissors used in r-DNA technology, cutting DNA at specific recognition sites. They are crucial for creating DNA fragments with either sticky or blunt ends, which is essential for gene cloning and manipulation.

🎯 Exam Tip: Remember to list a few specific restriction enzymes and clearly explain their role as "molecular scissors" in cutting DNA at precise recognition sites, distinguishing between blunt and sticky ends.

Question 8. Enlist and write in brief about the different biological tools required in r-DNA technology.
Answer:The biological tools used in r-DNA technology are various enzymes, cloning vectors and competent hosts.
(1) Enzymes:
• Enzymes like lysozymes, nucleases (exonucleases and endonucleases), DNA ligase, reverse transcriptase, DNA polymerase, alkaline phosphatases, etc. are used in r-DNA technology.
• The restriction endonucleases are used as biological or molecular scissors. They are able to cut a DNA molecule at a specific recognition site.
(2) Vectors:
• Vectors are DNA molecules which carry foreign DNA segment and replicate inside the host cell.
• Vectors may be plasmids, bacteriophages (M13, lambda virus), cosmid, phagemids, BAC (bacterial artificial chromosome), YAC (yeast artificial chromosome), transposons, baculoviruses and mammalian artificial chromosomes (MACs).
• Most commonly used vectors are plasmid vectors (pBR 322, pUC, Ti plasmid) and bacteriophages (lamda phage, M13 phage).
(3) Competent host cells:
1. They are bacteria like Bacillus haemophilus, Helicobacter pyroliand E. coli.
2. Mostly E. coli is used for the transformation with recombinant DNA.
In simple words: The three main tools for r-DNA technology are enzymes (for cutting, joining, and synthesizing DNA), vectors (to carry and replicate foreign DNA in host cells), and competent host cells (such as bacteria) that can take up and express the recombinant DNA.

🎯 Exam Tip: Clearly categorize the tools into enzymes, vectors, and host cells. For each category, provide examples and explain their specific function in the process of recombinant DNA technology.