**Biotechnology** is the integration of natural science and organisms (cells, parts thereof, and molecular analogues) for products and services. It encompasses both traditional processes (curd fermentation, bread-making, wine production) and modern molecular biotechnology (genetic engineering, gene therapy, DNA vaccines, in vitro fertilisation).
**Key distinction**: Traditional biotechnology uses naturally occurring microbes; modern biotechnology uses genetically modified organisms on larger scales.
**Two Core Techniques of Modern Biotechnology**:
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Traditional hybridisation in plant and animal breeding includes and multiplies undesirable genes along with desired ones. **Genetic engineering overcomes this limitation** by:
When alien DNA is transferred into an organism, it will **not multiply in progeny cells unless integrated into the genome**. The key requirement is:
**First Recombinant DNA (1972)**: Stanley Cohen and Herbert Boyer constructed the first recombinant DNA molecule by:
1. Isolating antibiotic resistance gene from *Salmonella typhimurium* plasmid
2. Cutting DNA using restriction enzymes (molecular scissors)
3. Linking the cut piece with plasmid DNA using DNA ligase
4. Transferring into *E. coli*, where plasmid acted as **vector** (carrier)
5. Creating **recombinant DNA** (new combination of autonomously replicating DNA created in vitro)
1. **Identification** of DNA with desirable genes
2. **Introduction** of identified DNA into the host
3. **Maintenance** of introduced DNA and transfer to progeny
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**Discovery**: First restriction endonuclease Hind II isolated and characterised in 1968; over 900 restriction enzymes known today from 230+ bacterial strains.
**Definition**: Restriction enzymes are molecular scissors that cut DNA at specific recognition sequences.
**Enzyme Naming Convention**:
**Classification of Nucleases**:
**Mechanism of Action**:
**Palindromic Sequences**: DNA sequences reading the same in 5' β 3' direction on both strands
**Sticky Ends**:
**Use in Genetic Engineering**: Creating recombinant DNA molecules (DNA from different sources) by:
**Principle**: DNA fragments are negatively charged and migrate toward anode under electric field through a medium.
**Matrix Used**: **Agarose** (natural polymer from sea weeds) β provides sieving effect
**Separation Logic**:
**Detection Process**:
1. Stain DNA with **ethidium bromide**
2. Expose to UV radiation
3. Visualise bright orange bands
**Elution**: Cutting and extracting DNA bands from agarose gel for use in recombinant DNA construction
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**Definition**: Plasmids and bacteriophages that replicate within bacterial cells independent of chromosomal DNA control, used to carry and multiply alien DNA.
**Copy Numbers**:
**Features Required for Cloning Vectors**:
**1. Origin of Replication (ori)**
**2. Selectable Marker**
**Example β pBR322 Vector Antibiotic Selection**:
**3. Cloning Sites**
**Alternative Marker System β Blue-White Screening**:
**4. Vectors for Plants and Animals**
**Agrobacterium tumefaciens Ti Plasmid** (Plant Vector):
**Retroviruses** (Animal Vector):
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**Problem**: DNA is hydrophilic (water-loving) and **cannot pass through cell membranes** directly.
**Solution**: Make bacterial cells **competent** (able to take up DNA) by:
**Transformation**: Procedure through which DNA piece is introduced into host bacterium; cells take up plasmid DNA.
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| Tool | Function | Key Feature |
|------|----------|-------------|
| **Restriction Enzymes** | Cut DNA at recognition sequences | Create sticky ends for joining |
| **DNA Ligase** | Joins cut DNA ends | Links alien DNA to vector |
| **Gel Electrophoresis** | Separates DNA fragments by size | Uses agarose matrix; visualised with ethidium bromide |
| **Plasmids (Vectors)** | Carry and replicate alien DNA | Have ori, selectable marker, cloning sites |
| **Bacteriophages (Vectors)** | High copy number DNA delivery | Multiple genome copies per cell |
| **Competent Cells** | Accept foreign DNA | Treated with CaΒ²βΊ to increase DNA uptake |
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This completes the comprehensive coverage of **Biotechnology: Principles and Processes** for CBSE Class 12 board exam preparation.
Q1. Restriction enzymes discovered by Herbert Boyer have the ability to cut DNA at specific locations and produce which of the following?
Answer: B β Restriction enzymes create sticky ends on DNA strands, which are complementary single-stranded overhangs that allow precise joining of DNA fragments from different sources.
Q2. A plasmid is described as an ideal vector for recombinant DNA technology because it:
Answer: B β Plasmids are autonomously replicating circular DNAs that float freely in bacterial cytoplasm, making them ideal vectors as they can carry and independently replicate alien DNA inserted into them.
Q3. Why is the origin of replication essential for the multiplication of alien DNA in a host organism?
Answer: B β The origin of replication is a specific DNA sequence responsible for initiating replication; when alien DNA is linked to it, the alien DNA becomes part of a chromosome and replicates along with host DNA.
Q4. The enzyme DNA ligase plays which role in the construction of recombinant DNA?
Answer: B β DNA ligase acts on cut DNA molecules and joins their ends, enabling the linking of an alien DNA fragment to a plasmid vector to create recombinant DNA.
Q5. In the historic 1972 experiment by Cohen and Boyer, the antibiotic resistance gene was transferred into E. coli using a plasmid vector from Salmonella typhimurium. What was the primary advantage of this approach over traditional hybridisation?
Answer: A β Genetic engineering via restriction enzymes and plasmids allows transfer of only the desired gene without undesirable genes, overcoming the limitation of traditional breeding where unwanted genes are multiplied along with desired ones.
Q6. A piece of alien DNA is introduced into a bacterial cell but fails to replicate in the progeny. Which of the following is the most likely reason?
Answer: B β Alien DNA must integrate into the host chromosome, which contains an origin of replication; without integration and this sequence, the alien DNA cannot replicate and is lost in progeny cells.
Q7. Which of the following statements is INCORRECT regarding the principles of biotechnology?
Answer: C β Asexual reproduction preserves genetic information without variation, whereas sexual reproduction and especially genetic engineering enable genetic variation and new combinations; the statement incorrectly claims asexual reproduction provides more variation.
Q8. Consider two statements: (Assertion) Sticky ends produced by restriction enzymes are crucial for recombinant DNA formation. (Reason) Sticky ends are complementary single-stranded overhangs that allow precise joining of DNA fragments from different sources. Which of the following is correct?
Answer: A β Sticky ends are indeed crucial for recombinant DNA formation because their complementary nature enables precise and specific joining of DNA fragments, making the reason a correct explanation of the assertion.
Q9. If a plasmid vector has a molecular weight of 5 kb (kilobases) and an alien DNA fragment is 8 kb, the resulting recombinant DNA molecule would have a molecular weight of approximately:
Answer: C β When an alien DNA fragment (8 kb) is joined to a plasmid vector (5 kb) using DNA ligase, the total molecular weight of the resulting recombinant DNA is the sum: 5 + 8 = 13 kb.
Q10. The European Federation of Biotechnology (EFB) definition of biotechnology as 'integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services' encompasses both traditional and modern biotechnology. Why is making curd using Lactobacillus considered biotechnology under this definition, even though it predates modern genetic engineering?
Answer: B β The EFB definition is broad and inclusive; making curd uses living Lactobacillus organisms to produce a useful product through fermentation, fitting the definition of integrating organisms for products and services, making it biotechnology even without genetic modification.
What are restriction enzymes and what is their key property discovered by Boyer?
Restriction enzymes are 'molecular scissors' that cut DNA at specific locations and create sticky ends, allowing precise DNA fragments to be joined together.
Define recombinant DNA and state when it was first created.
Recombinant DNA is a new combination of circular autonomously replicating DNA created in vitro by joining an alien DNA fragment to a plasmid vector, first accomplished by Cohen and Boyer in 1972.
What is the role of the origin of replication in genetic engineering?
The origin of replication is a specific DNA sequence in chromosomes that initiates replication, allowing alien DNA linked to it to be copied and inherited in the host organism.
What is the function of DNA ligase in constructing recombinant DNA?
DNA ligase is an enzyme that joins the cut ends of DNA molecules together, making it possible to link an alien DNA fragment to a plasmid vector.
Why is a plasmid considered a suitable vector for transferring alien DNA?
A plasmid is a suitable vector because it is a small, autonomously replicating circular DNA that can carry alien genes into a host cell and replicate independently from chromosomal DNA.
What is the difference between genetic engineering and bioprocess engineering?
Genetic engineering alters DNA chemistry to change an organism's phenotype, while bioprocess engineering maintains sterile conditions to grow desired microbes or cells in large quantities for product manufacture.
How does genetic engineering overcome the limitation of traditional hybridisation breeding?
Genetic engineering allows isolation and transfer of only desired genes without undesirable genes, whereas traditional hybridisation often multiplies undesirable genes along with desired ones.
What is cloning in the context of biotechnology?
Cloning is the process of making multiple identical copies of any template DNA so it can be replicated and inherited in the host organism.
What does the European Federation of Biotechnology (EFB) define biotechnology as?
The EFB defines biotechnology as the integration of natural science and organisms, cells, parts thereof, and molecular analogues for products and services.
Why must alien DNA inserted into a host organism become integrated into its genome?
Alien DNA must integrate into the genome so it becomes part of a chromosome with an origin of replication, enabling it to replicate and be inherited in progeny cells.
Define recombinant DNA and state the year in which the first recombinant DNA was constructed. Name the two scientists responsible for this achievement. [2 marks]
Recombinant DNA is a new circular DNA created in vitro by joining alien DNA to a plasmid vector; constructed in 1972 by Cohen and Boyer using restriction enzymes and DNA ligase.
Explain why origin of replication is essential for the multiplication and inheritance of alien DNA in a host organism. Describe the role of each component in creating recombinant DNA: restriction enzymes, plasmid vectors, and DNA ligase. [5 marks]
Origin of replication initiates DNA copying and allows alien DNA integrated into chromosomes to replicate; restriction enzymes cut DNA at specific sites creating sticky ends; plasmid vectors carry alien DNA; DNA ligase joins cut DNA ends. Show how these work together: cutting β linking to plasmid β integration β replication.
Genetic engineering overcomes the limitations of traditional hybridisation in plant and animal breeding. Explain how this is achieved by describing the three basic steps of genetic modification and compare the outcomes with traditional breeding. Include the significance of being able to isolate and transfer only desired genes without undesirable genes. [6 marks]
Three steps: (1) isolation of desired genes using restriction enzymes, (2) cloning via plasmid vectors and DNA ligase creating recombinant DNA, (3) transfer and expression in host organism. Traditional breeding multiplies undesirable genes along with desired; genetic engineering transfers only target genes via origin of replication integration, providing precise genetic combinations and phenotypic changes without genetic load.
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