Biotechnology

Part III · Common Biology · Chapter Thirteen

Expect 7–10 questions: restriction enzymes (Type II, recognition sequences, sticky/blunt ends), PCR (temperatures, Taq polymerase, variants), cloning vectors (plasmid vs BAC vs YAC capacities), Bt crops (cry genes, India approval dates), Agrobacterium Ti-plasmid mechanism, Human Genome Project, CRISPR-Cas9 Nobel, recombinant insulin, and HP-specific items (CSIR-IHBT Palampur tea genome, Picrorhiza kurroa tissue culture, micropropagation labs at Junga & Mashobra). Discovery-year “Nobel” pairings are reliably tested.

Read · 75 min
Revise · 20 min
MCQs · 27

Syllabus Coverage

Principles and tools of recombinant DNA technology • Restriction enzymes, ligases, and gel electrophoresis • PCR and its variants • Cloning vectors (plasmids, phage λ, cosmids, BAC, YAC) • Host systems • Gene expression analysis, hybridisation blots, genomics • Transgenic plants: Bt crops, Golden Rice, Flavr Savr • Agrobacterium-mediated and biolistic plant transformation • Transgenic animals, gene therapy, CRISPR-Cas9 • Industrial biotechnology: fermentation, antibiotics, recombinant pharmaceuticals • Plant tissue culture and totipotency • Biofertilisers.

13.1 Foundations & Tools of rDNA Technology

Biotechnology is the controlled use of living organisms or their products to modify, improve, or manufacture useful goods and services. Its modern molecular form rests on the ability to cut DNA at precise sites, join fragments from different sources, and express the resulting recombinant DNA (rDNA) in a host organism. This section surveys the tools that make rDNA technology possible.

Watson & Crick — double-helix structure of DNA, 1953 (Nobel 1962) · Khorana — chemical synthesis of oligonucleotides & genetic code, 1968 (Nobel 1968) · Smith & Wilcox — first restriction enzyme HindII isolated from H. influenzae, 1970 · Arber, Smith, Nathans — Nobel 1978 for restriction enzymes · Berg — first recombinant DNA molecule (SV40 + λ DNA), 1972 (Nobel 1980) · Cohen & Boyer — first DNA cloning using plasmid pSC101, 1973 · Sanger — DNA sequencing by chain termination, 1977 (Nobel 1980, his second!) · Mullis — PCR, 1983 (Nobel 1993) · Doudna & Charpentier — CRISPR-Cas9 gene editing, 2012 (Nobel 2020) · Wilmut et al. — Dolly the sheep, first cloned mammal by SCNT, 1996

Recombinant DNA

A DNA molecule formed by joining DNA sequences from two or more different sources — typically using restriction endonucleases to cut and DNA ligase to seal — so that new genetic combinations arise that do not occur naturally. The term encompasses the molecule itself and the entire technology of creating, propagating, and expressing it.

13.1.1 Restriction Endonucleases

Restriction endonucleases are bacterial enzymes that cleave double-stranded DNA at or near specific short palindromic sequences (4–8 bp). They evolved as a defence against foreign phage DNA (restriction-modification system): the bacterium methylates its own recognition sites, but unmethylated phage DNA is cleaved. Three classes are recognised by their subunit composition and cleavage position relative to the recognition site.

Easy to confuse — Type I vs Type II vs Type III Restriction Enzymes

Type I

Single multi-subunit enzyme with restriction and methyltransferase activities. Cuts far from recognition site (1000+ bp away). Requires ATP, AdoMet, Mg²⁺. Not used in cloning.

Type II

Separate restriction and methylase enzymes. Cuts within or adjacent to the palindromic recognition site. Generates reproducible fragments. Standard cloning tools. Examples: EcoRI, BamHI, HindIII.

Type III

Cleaves ~25–27 bp downstream of recognition site on one strand. Requires ATP. Produces short 5′ overhangs. Not widely used in routine cloning.

Palindromic sequences read the same on both strands in the 5′→3′ direction. For example, the EcoRI recognition site 5′-GAATTC-3′ is matched by 3′-CTTAAG-5′ on the complementary strand (also 5′-GAATTC-3′ when read 5′→3′). EcoRI cuts between the G and A on both strands, generating a 4-base 5′-overhang (“sticky end”): 5′-G / AATTC-3′. Sticky ends greatly increase ligation efficiency because complementary single-stranded tails anneal by hydrogen bonds before the ligase seals them.

Easy to confuse — Cohesive (Sticky) Ends vs Blunt Ends

Cohesive (Sticky) Ends

Staggered cuts leave single-stranded overhangs: 5′-overhang (EcoRI, BamHI) or 3′-overhang (PstI, KpnI). The overhangs base-pair with complementary sticky ends from any source. Ligate efficiently; may re-circularise.

Blunt Ends

Both strands cut at same position: no overhang. Produced by SmaI (CCC↓GGG), EcoRV, HincII (HindII). Ligate less efficiently but allow joining of any two blunt-ended fragments regardless of sequence. T4 DNA ligase can ligate blunt ends.

**Table 13.1**Common Type II restriction enzymes — recognition sequences & end types
Enzyme	Source organism	Recognition sequence (5′→3′)	Cut site	End type
EcoRI	E. coli RY13	5′…G↓AATTC…3′	Staggered (5′ overhang)	Sticky
BamHI	B. amyloliquefaciens H	5′…G↓GATCC…3′	Staggered (5′ overhang)	Sticky
HindIII	H. influenzae Rd	5′…A↓AGCTT…3′	Staggered (5′ overhang)	Sticky
PstI	P. stuartii	5′…CTGCA↓G…3′	Staggered (3′ overhang)	Sticky
SalI	S. albus	5′…G↓TCGAC…3′	Staggered (5′ overhang)	Sticky
SmaI	S. marcescens	5′…CCC↓GGG…3′	Flush	Blunt
EcoRV	E. coli J62	5′…GAT↓ATC…3′	Flush	Blunt
HindII	H. influenzae Rd (Smith, 1970)	5′…GTY↓RAC…3′	Flush	Blunt (first ever)

Mnemonic — Restriction Enzyme Palindromes

"Every Bad Student Passes Happily" → EcoRI · BamHI · SmaI · PstI · HindIII — the five most-tested enzymes. To remember EcoRI cuts 5′…G|AATTC…3′: the palindrome G-A-A-T-T-C has 6 letters (hexanucleotide); the stagger leaves a 4-base overhang (AATT). Same logic: BamHI is G|GATCC (overhang GATC, 4 bases).

13.1.2 DNA Ligase

T4 DNA ligase (encoded by bacteriophage T4 gene 30) catalyses formation of phosphodiester bonds between adjacent 3′-OH and 5′-phosphate termini, using ATP as cofactor. It joins complementary sticky ends (after they anneal) or blunt ends (less efficiently). In vivo, E. coli DNA ligase uses NAD⁺ as cofactor. T4 ligase is the universal tool in molecular cloning because it seals both sticky and blunt ends.

13.1.3 Gel Electrophoresis

Nucleic acid fragments in a gel are separated by size under an electric field: the negatively charged sugar-phosphate backbone migrates toward the positive pole; smaller fragments move faster (higher mobility through the porous gel matrix). Agarose gel (0.5–2 % for DNA/RNA, 0.7–3 % for RNA) is standard; SDS-PAGE (polyacrylamide denaturing gel) separates proteins by molecular weight. Stains: ethidium bromide (intercalates, visualised under UV — mutagenic, fume-hood essential) or SYBR Green (safer, more sensitive).

Restriction digests are run on agarose alongside a DNA ladder (size markers). The pattern of bands is the restriction map — unique to each DNA source, and the basis of early DNA fingerprinting. For preparative purposes, the band can be excised from the gel and purified.

Fig. 13.1 EcoRI cuts the palindrome G↓AATTC on both strands, creating 4-nucleotide 5′-overhang sticky ends. The linearised plasmid and a foreign insert with compatible ends are annealed and sealed by T4 DNA ligase to produce a recombinant plasmid, which is then transformed into a host bacterium.

13.2 PCR and Amplification Techniques

The Polymerase Chain Reaction (PCR), developed by Kary B. Mullis in 1983 (Nobel Prize in Chemistry, 1993), exponentially amplifies a specific DNA sequence defined by two oligonucleotide primers. Starting from even a single molecule, 30 PCR cycles produce approximately 2³⁰ ≈ 10⁹ copies — enough for gel analysis, sequencing, cloning, or forensic profiling. The reaction exploits the heat-stable Taq DNA polymerase isolated from the thermophilic bacterium Thermus aquaticus, which thrives in Yellowstone hot springs at 70–75 °C.

13.2.1 The Three-Step Cycle

_m − 5 °C) Forward primer Reverse primer Primers bind complementary sequences flanking target Step 3 — Extension 72 °C ~1 min per kb (Taq) new strand Taq polymerase adds dNTPs 5′→3′ from primer Optimal temp 72 °C Repeat × 30 cycles

Fig. 13.2 The PCR cycle. Each cycle doubles the number of target copies: (1) 94–96 °C denaturation separates the double helix; (2) cooling to ~50–65 °C allows specific primer annealing; (3) 72 °C extension by Taq polymerase synthesises the new strand. After 30 cycles: 2³⁰ ≈ 10⁹ copies.

13.2.2 Key Components

Template DNA — as little as a single copy; any source (fresh, dried, ancient, degraded).
Primers — two oligonucleotides (~18–25 bp) complementary to flanking sequences on opposite strands. They determine specificity and define the amplicon boundaries.
Taq polymerase — thermostable; active at 72 °C; lacks 3′→5′ proofreading exonuclease (error rate ~10⁻⁵); adds a single 3′-A overhang. Proofreading polymerases (Pfu, Phusion) used when fidelity is critical.
dNTPs — equimolar mix of dATP, dCTP, dGTP, dTTP as building blocks.
Buffer + Mg²⁺ — MgCl₂ is essential cofactor for polymerase activity; its concentration affects primer annealing stringency.
Thermal cycler — automated programmable heat block for rapid temperature changes.

Easy to confuse — PCR vs RT-PCR vs qPCR (Real-Time PCR)

Standard PCR

Template: DNA. Product detected after amplification by gel electrophoresis. Qualitative (presence/absence) or rough quantity by band intensity. Used in: diagnostics, DNA fingerprinting, cloning, genotyping.

RT-PCR

Template: RNA reverse-transcribed to cDNA first (by reverse transcriptase), then amplified. Detects mRNA expression. Key use: COVID-19 diagnosis (SARS-CoV-2 RNA detected by RT-PCR). Also used for gene expression studies and virological surveillance.

qPCR / Real-Time PCR

Quantitative. Fluorescent signal (SYBR Green or TaqMan probe) monitored each cycle. Cycle threshold (C_t) value inversely proportional to starting template amount. Combines with reverse transcription as RT-qPCR for mRNA quantification.

Exam Tip: The acronym PCR was coined by Mullis himself. Taq polymerase is unique in being heat-stable; earlier PCR experiments used mesophilic Klenow fragment, requiring re-addition after each denaturation step. The commercial version of Taq is sold as a recombinant protein (expressed in E. coli). Nested PCR uses two successive amplifications with inner primers for increased specificity; multiplex PCR uses multiple primer pairs in one tube for several targets simultaneously.

Worked Example — Calculating PCR Product Yield

"You set up a PCR with 1 template molecule and run 30 cycles. Assuming 100% efficiency per cycle, how many double-stranded amplicon copies are produced?"

Strategy: Each cycle doubles the number of copies (provided there are no substrate limitations). After n cycles starting from 1 molecule: copies = 2ⁿ. After 30 cycles: 2³⁰ = 1,073,741,824 ≈ 10⁹ copies. In practice, efficiency per cycle is ~80–90%, so the observed yield is somewhat less. The exponential amplification is why PCR can detect even a single copy of pathogen DNA in a clinical sample.

13.3 Cloning Vectors & Host Systems

A cloning vector is a DNA molecule capable of autonomous replication in a host cell and of carrying foreign DNA inserts. The ideal vector has: (i) an origin of replication (ori) for propagation; (ii) a selectable marker (antibiotic resistance) to identify transformed cells; (iii) unique restriction sites in a multiple cloning site (MCS) for insert ligation; and optionally (iv) a reporter gene for blue-white screening. The choice of vector depends critically on insert size.

Easy to confuse — Plasmid vs Cosmid vs Phage λ vs BAC vs YAC

Plasmid

Small circular bacterial DNA. Self-replicating. Insert up to ~10 kb. Examples: pBR322 (Amp^r/Tet^r), pUC19 (lacα, MCS). Easiest to handle; most widely used.

Phage λ / Cosmid

Phage λ replacement vectors accept inserts of 9–23 kb; packaged in vitro into phage heads and infected into bacteria efficiently. Cosmids (plasmid + λ cos sites) carry 35–50 kb; replicate as plasmids but are packaged as phage.

BAC / YAC

BAC (Bacterial Artificial Chromosome): 100–300 kb. Based on E. coli F-plasmid. Stable; used in Human Genome Project (HGP). YAC (Yeast Artificial Chromosome): up to 1 Mb (1000 kb). Contains yeast centromere, telomeres, ARS. Unstable (chimaeric inserts); used for large eukaryotic loci.

**Table 13.2**Cloning vector capacities at a glance
Vector type	Insert capacity	Host	Application
Plasmid (pUC, pBR322)	Up to ~10 kb	E. coli	Subcloning, gene expression
Phage λ replacement	9–23 kb	E. coli	Genomic libraries
Cosmid	35–50 kb	E. coli	Large gene clusters
Phagemid	Up to ~10 kb	E. coli	ssDNA production
BAC	100–300 kb	E. coli	HGP physical map, libraries
YAC	100–1000+ kb	S. cerevisiae	Mega-base cloning, HGP
Ti plasmid (Agrobacterium)	~5–30 kb insert in T-DNA	Dicot plants	Plant transformation
Viral (AAV, lentivirus)	~4 kb (AAV); ~8 kb (lenti)	Mammalian	Gene therapy

13.3.1 Plasmid pBR322 and pUC Vectors

pBR322 (Bolivar & Rodriguez, 1977) is a 4361 bp plasmid of historical and didactic importance. It carries two selectable markers: ampicillin-resistance (bla) and tetracycline-resistance (tet). An insert cloned into the unique HindIII site (within tet) disrupts tetracycline resistance, enabling insertional inactivation screening: Amp^r Tet^s colonies carry insert; Amp^r Tet^r colonies do not. pUC19 improves on pBR322 with a higher copy number (ColE1 ori), a shorter 2686 bp backbone, and the lacZα system for blue-white screening: intact lacZα on vector + X-gal substrate → blue colony; insert disrupting lacZα → white colony (recombinant).

Easy to confuse — Selectable Marker vs Reporter Gene

Selectable Marker

Confers growth advantage (or survival) in selective medium. Antibiotic resistance (amp^r, kan^r, tet^r, hygro). Used to select transformed cells from un-transformed background. Required in all vectors.

Reporter Gene

Produces a detectable signal (colour, fluorescence, luminescence). lacZα (blue/white); GUS (β-glucuronidase; plant expression); GFP (green fluorescent protein; live-cell imaging); luc (luciferase; bioluminescence). Used to confirm gene expression, not selection.

13.3.2 Host Systems

The most common prokaryotic host is Escherichia coli strain DH5α or TOP10 for cloning, and BL21 (DE3) for T7-promoter-driven protein expression: cheap, rapid (20 min doubling), well-characterised genetics, easily transformed. Limitations: no eukaryotic post-translational modifications (glycosylation, disulphide bonds); inclusion body formation for many eukaryotic proteins.

Saccharomyces cerevisiae (baker's yeast) is the workhorse eukaryotic host: performs N-glycosylation, protein folding with chaperones, and disulphide bonding. Used for insulin precursors, hepatitis B surface antigen vaccine. Insect cell systems (Sf9 cells with baculovirus vector) give complex glycosylation. Mammalian cells (CHO = Chinese Hamster Ovary; HEK293 = Human Embryonic Kidney) produce the most authentic post-translational modifications and are used for complex therapeutics (monoclonal antibodies, EPO, factor VIII).

Worked Example — Choosing a Suitable Vector for a Given Insert

"A researcher wishes to clone a 180 kb genomic segment carrying the human dystrophin locus. Which vector is most appropriate?"

Strategy: Insert size 180 kb exceeds plasmid (~10 kb), phage λ (23 kb), and cosmid (50 kb) capacities. BAC handles 100–300 kb stably in bacteria and was used for the Human Genome Project. YAC can hold 180 kb but is prone to chimaeric inserts. Answer: BAC is the preferred choice for genomic inserts of 100–300 kb requiring stability. YAC would be the backup if coverage of very large segments (>500 kb) is needed.

13.4 Gene Expression Analysis & Genomics

Knowing whether a cloned gene is expressed requires tools that detect specific nucleic acid sequences or proteins in complex mixtures. The hybridisation blot methods — Southern (1975), Northern, Western — remain cornerstones of molecular biology, though they have been largely supplanted by sequencing-based approaches for genomic work.

Easy to confuse — Southern vs Northern vs Western vs Eastern Blot

Southern Blot

Target: DNA. Edwin Southern, 1975. DNA fragments separated by agarose gel electrophoresis → denatured in situ → transferred to nitrocellulose/nylon membrane → hybridised with labelled probe. Detects specific gene sequences, restriction fragment length polymorphisms (RFLPs). Used in DNA fingerprinting, genotyping.

Northern Blot

Target: RNA. Named by analogy with Southern (no discoverer named Northern). Denaturing gel → membrane → RNA probe hybridisation. Detects mRNA expression level and transcript size. Useful for splicing variants. Largely replaced by RT-qPCR and RNA-seq.

Western / Eastern Blot

Western: Target = protein. SDS-PAGE → transfer to membrane → antibody probing. Also called immunoblotting. Detects specific proteins. Used in HIV diagnosis (confirmatory), prion detection, protein expression analysis. Eastern: detects post-translational modifications (e.g., phosphorylation, glycosylation) on proteins after Western-style transfer.

Mnemonic — Blot Methods

"Some Nights We Eat" → Southern (DNA) · Northern (RNA) · Western (protein) · Eastern (post-translational mods). Remember: Southern is the only one named after an actual person (Edwin Southern). The others are compass-point jokes.

13.4.1 DNA Sequencing

Sanger sequencing (chain-termination method, 1977) uses dideoxy chain terminators (ddNTPs) to produce a nested set of fragments of all lengths; these are separated by electrophoresis and the sequence read from the terminating ddNTP at each position. Frederick Sanger received his second Nobel Prize in Chemistry 1980 for this work (first was for protein sequencing, 1958 — one of only four persons to win two Nobel Prizes). Sanger sequencing produces reads of ~700–1000 bp and dominated for two decades.

Next-Generation Sequencing (NGS) platforms massively parallelise the reaction: Illumina (sequencing by synthesis with reversible terminators) produces hundreds of millions of 150 bp reads per run; PacBio (SMRT sequencing) and Oxford Nanopore give long reads of tens of kilobases. The entire 3-billion-base human genome was first completed in 2003 (after 13 years); today the same can be done in under 24 hours on a single instrument.

13.4.2 Genomic Library vs cDNA Library

Easy to confuse — Genomic Library vs cDNA Library

Genomic Library

Represents the entire genome: coding + non-coding + intronic + regulatory sequences. Constructed by partially digesting total genomic DNA with a restriction enzyme, cloning all fragments into a vector (phage λ or BAC). Contains introns; useful for studying gene structure, promoters, regulatory elements.

cDNA Library

Represents only expressed sequences: mRNA is reverse-transcribed to cDNA by reverse transcriptase (Temin & Baltimore, Nobel 1975), then cloned. No introns; tissue- and condition-specific. Preferred for cloning eukaryotic protein-coding genes for expression in E. coli (which cannot splice introns).

13.4.3 DNA Microarray

A DNA microarray (DNA chip) carries thousands to millions of oligonucleotide probes fixed at defined positions on a glass slide. Fluorescently labelled cDNA from an experimental and a control sample are hybridised simultaneously (two-colour arrays) or separately (single-channel). The ratio of fluorescent signals indicates up- or down-regulation of each gene. Affymetrix GeneChips cover the entire human transcriptome (>30,000 genes). Microarrays enabled the first genome-wide expression profiling studies in cancer biology. They have been partly succeeded by RNA-seq but remain used in clinical diagnostics.

13.4.4 Human Genome Project (HGP)

The HGP ran from 1990 to 2003, coordinating sequencing centres in the USA, UK, France, Germany, Japan, and China (international public consortium) alongside the private effort by Celera Genomics (Craig Venter). Key findings: ~3.2 billion base pairs; ~20,000–25,000 protein-coding genes (far fewer than predicted); only ~1.5% of the genome codes for proteins; repeat elements constitute >50% of the genome. The physical map used BAC clones; sequence was assembled by whole-genome shotgun (Celera) and hierarchical shotgun (public consortium) strategies. India participated through CSIR laboratories. CSIR-IHBT Palampur later contributed to the sequencing of the tea genome (Camellia sinensis var. assamica, 2017) — an important HP research milestone.

**Table 13.3**Omics disciplines — scope and tools
Discipline	Molecule studied	Key tools	Output
Genomics	Complete DNA (genome)	NGS, bioinformatics, BAC/YAC libraries	Gene catalogue, structural variation
Transcriptomics	All RNA (transcriptome)	RNA-seq, microarray, Northern blot, qPCR	Gene expression profiles
Proteomics	All proteins (proteome)	2D-PAGE, mass spectrometry, Western blot	Protein abundance, interactions
Metabolomics	Small-molecule metabolites	NMR, LC-MS, GC-MS	Metabolic state, biomarkers
Epigenomics	Chromatin marks, methylation	ChIP-seq, ATAC-seq, bisulphite sequencing	Regulatory landscape

HP Angle: CSIR-IHBT Palampur (Institute of Himalayan Bioresource Technology) is India's premier hill-region biotechnology institute. Key contributions include: sequencing the Camellia sinensis var. assamica (Assam tea) genome (2017); development of high-value medicinal plant tissue culture protocols including Picrorhiza kurroa (kutki) and Taxus species; phytochemical profiling of HP medicinal plants. In HPRCA exams, IHBT Palampur may appear in questions on tea biotechnology, genomics institutions, or medicinal plant conservation.

13.5 Transgenic Plants & Bt Crops

A transgenic plant contains a stably integrated foreign gene (“transgene”) in its nuclear or plastid genome that is heritably expressed. Commercial transgenic crop development began in the 1990s and has grown to over 190 million hectares globally, primarily in the Americas, India, and China. India's regulatory authority for GM crops is the Genetic Engineering Appraisal Committee (GEAC) under the Ministry of Environment.

13.5.1 Bt Crops — Mechanism

Bacillus thuringiensis (Bt) is a Gram-positive spore-forming soil bacterium that produces insecticidal crystal (Cry) proteins — δ-endotoxins — during sporulation. The cry genes encode protoxins (128–140 kDa) stored as crystalline inclusions. When ingested by susceptible insects, the alkaline midgut pH (~10) dissolves the crystals; gut proteases cleave the protoxin to an active toxin (~65 kDa) that binds specific glycoprotein receptors on midgut epithelial cell brush-border membranes, inserts into the membrane, and forms lytic pores, causing osmotic shock, cell lysis, gut paralysis, and death.

Fig. 13.3 Bt cotton mechanism. The Cry1Ac/Cry2Ab protoxin crystal in plant tissue is ingested by the bollworm, dissolved in the alkaline midgut, proteolytically activated, bound to cadherin receptors, and inserted into the epithelial membrane to form lytic pores, leading to insect death. Non-target mammals are unaffected due to acidic gut pH and receptor absence.

13.5.2 Other Important Transgenic Crops

**Table 13.4**Key transgenic crops — gene, trait, and status
Crop	Transgene(s)	Trait conferred	Year / Status
Bt cotton (Bollgard)	cry1Ac, cry2Ab (Bt)	Bollworm resistance	India 2002 (Bollgard-I); 2006 (Bollgard-II)
Roundup Ready soybean	EPSPS from Agrobacterium	Glyphosate (herbicide) tolerance	USA 1996; global leader in adoption
Golden Rice	psy (daffodil) + crtI (bacterium)	β-carotene synthesis (pro-vitamin A)	Ingo Potrykus & Peter Beyer, 2000; regulatory approved in Philippines 2021
Flavr Savr tomato	Antisense polygalacturonase	Delayed softening/ripening	First GM food; USA 1994; withdrawn 1997
Bt brinjal	cry1Ac	Shoot & fruit borer resistance	Bangladesh commercial 2014; India moratorium since 2010
Herbicide-tolerant maize	pat / bar gene	Glufosinate tolerance	USA, EU — widely adopted

13.5.3 Methods of Plant Transformation

Fig. 13.4 Agrobacterium-mediated plant transformation. The disarmed Ti plasmid carries the gene of interest flanked by T-DNA border sequences. Wounded plant tissue releases phenolic signals (acetosyringone) that activate vir genes, causing excision of T-DNA and its transfer into the plant cell nucleus, where it integrates randomly into a chromosome. Transgenic cells are selected and regenerated into whole plants via tissue culture.

Exam Tip: Agrobacterium is a natural genetic engineer — it evolved T-DNA transfer to make the plant produce opines (nutritive compounds) for the bacterium. In the engineered vector, tumour-inducing genes (ipt, iaa) are removed and replaced with the gene of interest. The T-DNA border sequences (25 bp direct repeats) are the only cis-elements required for transfer; the vir genes act in trans and can be on a separate helper plasmid (binary vector system).

Easy to confuse — Agrobacterium vs Particle Bombardment (Biolistics)

Agrobacterium-Mediated

Natural biological delivery. Works well for most dicots. Integrates T-DNA at single or few loci. Lower copy number. Stable inheritance. Most commercially used method for cotton, tobacco, potato, tomato.

Particle Bombardment (Gene Gun)

DNA coated on gold/tungsten microparticles, accelerated at high pressure into plant cells. Works for monocots (rice, wheat, maize) and recalcitrant species. Higher copy number, multiple insertion loci, higher silencing risk. Used for maize, wheat, rice, sorghum transformation.

13.6 Transgenic Animals & Gene Therapy

13.6.1 Transgenic Animals

A transgenic animal carries a stably integrated foreign gene in its germ line, so all cells (including gametes) contain the transgene and it is heritably transmitted. Methods include pronuclear microinjection (classical mouse transgenics), retroviral infection of embryos, and embryonic stem (ES) cell-based targeting for knockouts/knock-ins.

Pharming — transgenic cattle or goats express human proteins in milk: e.g., ATryn (antithrombin) from transgenic goats, the first FDA-approved drug from a transgenic animal (2009).
Spider-silk goats — silk protein gene in mammary gland promoter; silk protein purified from milk for ultrastrong fibres.
Knockout mice — a specific gene is disrupted by homologous recombination in ES cells (Capecchi, Evans, Smithies; Nobel 2007); used as disease models (cancer, Alzheimer's, cystic fibrosis).
Oncomouse — first patented animal (Harvard, 1988); carries activated myc oncogene in mammary tissue; used in cancer research.

13.6.2 Somatic Cell Nuclear Transfer (SCNT) and Dolly

Dolly the sheep (born 5 July 1996; died 14 February 2003 aged 6½), created by Ian Wilmut and colleagues at the Roslin Institute, Scotland, was the first mammal cloned from an adult somatic cell by SCNT. A nucleus from a mammary gland cell of a 6-year-old Finn Dorset ewe was transferred into an enucleated Scottish Blackface oocyte; the reconstructed embryo was implanted into a surrogate. Dolly demonstrated that a differentiated adult nucleus is fully totipotent when returned to an ooplasmic environment. Dolly suffered from premature ageing (shorter telomeres) and arthritis. SCNT has since been achieved in cattle, pigs, cats, dogs, horses, and primates.

Exam Tip: “Clonal” vs “transgenic” — a common confusion point. A cloned animal (e.g., Dolly) is a genetic copy of the donor but does not necessarily contain foreign DNA. A transgenic animal carries a foreign gene integrated into its genome but is not a clone of another individual. SCNT can produce either: a cloned transgenic animal if the donor nucleus already carries a transgene.

Easy to confuse — Clonal vs Transgenic Animal

Clonal Animal

Genetically identical (or near-identical) copy of a donor. Made by SCNT or embryo splitting. No foreign DNA necessarily. Example: Dolly. Purpose: animal propagation, preservation of elite genetics, research.

Transgenic Animal

Carries an integrated foreign gene (transgene) in germ line. Made by pronuclear microinjection, retroviral delivery, or ES-cell targeting. Example: Oncomouse, insulin-producing cattle, knockout mice. Purpose: disease models, biopharmaceutical production, gene function studies.

13.6.3 Gene Therapy

Gene therapy aims to correct genetic disease by introducing, altering, or suppressing gene expression in patient cells. Two broad approaches exist: somatic gene therapy (modification of non-germline cells; changes not inherited) and germline gene therapy (modification of sperm, egg, or early embryo; heritable; ethically controversial and prohibited in most countries).

The first approved gene therapy trial was in 1990 for ADA-SCID (severe combined immunodeficiency due to adenosine deaminase deficiency) — W. French Anderson at NIH. T lymphocytes from the patient were transduced with a retroviral vector carrying the normal ADA gene and reinfused. Today gene therapy vectors include: retroviruses and lentiviruses (integrating; risk of insertional mutagenesis), adeno-associated virus (AAV) (non-integrating; low immunogenicity; most widely used in clinical trials), adenovirus (non-integrating; transient; strong immune response), and ex vivo approaches with CRISPR editing.

13.6.4 CRISPR-Cas9

CRISPR-Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats & CRISPR-associated protein 9), developed as a gene-editing tool by Jennifer Doudna (UC Berkeley) and Emmanuelle Charpentier (Umea University/Helmholtz Berlin) in 2012 (Nobel Prize in Chemistry 2020), is an RNA-guided endonuclease system derived from the bacterial adaptive immune system. A single guide RNA (sgRNA) directs the Cas9 nuclease to a complementary genomic locus (20 bp target adjacent to a PAM sequence 5′-NGG-3′), where Cas9 makes a double-strand break (DSB). The cell repairs the DSB by error-prone NHEJ (causing indels → gene knockout) or by precise homology-directed repair (HDR) using a provided template (gene correction or insertion).

Applications: CAR-T cell cancer immunotherapy (ex vivo editing of T cells), sickle-cell disease correction (Casgevy, first CRISPR drug approved 2023), anti-viral strategies, crop improvement, and basic research.

Exam Tip: Nobel 2020 for CRISPR-Cas9 went to Doudna and Charpentier (both women — the only all-female Nobel science laureates to date). The first CRISPR gene therapy drug, Casgevy (exa-cel), approved by FDA and UK MHRA in November–December 2023 for sickle-cell disease and β-thalassaemia, is a landmark in translational biotechnology. Examiners may test the year, developers, or the PAM sequence (5′-NGG-3′) for Cas9.

13.7 Industrial Biotechnology — Fermentation, Enzymes & Pharmaceuticals

Industrial (white) biotechnology harnesses microbial or enzymatic processes to manufacture chemicals, fuels, pharmaceuticals, and food ingredients at scale. Fermentation — the controlled cultivation of microorganisms (or cells) in bioreactors to produce desired metabolites — is the central unit operation.

13.7.1 Antibiotics

Antibiotics are low-molecular-weight secondary metabolites produced by microorganisms that inhibit or kill other microorganisms. The term was coined by Selman Waksman (1942), who also discovered streptomycin (Nobel 1952). Commercial antibiotic production uses submerged fermentation in stirred-tank bioreactors with carefully controlled pH, temperature, aeration, and feed rate.

**Table 13.5**Major antibiotics — producers and targets
Antibiotic	Producer organism	Year (discovery)	Mechanism
Penicillin	Penicillium notatum / P. chrysogenum	Fleming 1928; Florey & Chain 1940 (Nobel 1945)	Inhibits peptidoglycan transpeptidase (β-lactam)
Streptomycin	Streptomyces griseus	Waksman 1943 (Nobel 1952)	Binds 30S ribosomal subunit; misreading
Tetracycline	S. aureofaciens	Duggar 1948	Blocks aminoacyl-tRNA binding to 30S
Erythromycin	S. erythraeus	McGuire 1952	Binds 23S rRNA; blocks translocation
Chloramphenicol	S. venezuelae	Burkholder 1947	Inhibits peptidyl transferase (50S)
Cephalosporin	Acremonium chrysogenum	Brotzu 1945	β-lactam; cell wall synthesis
Griseofulvin	Penicillium griseofulvum	Oxford 1939	Inhibits microtubule polymerisation (antifungal)

13.7.2 Industrial Organic Acids and Other Metabolites

Citric acid — Aspergillus niger (90 % of world production; added to foods, beverages, pharmaceuticals)
Lactic acid — Lactobacillus spp. (yoghurt, cheese, biodegradable PLA polymer)
Gluconic acid — Aspergillus niger / Gluconobacter
Itaconic acid — Aspergillus terreus (bioplastic precursor)
Ethanol (bioethanol) — Saccharomyces cerevisiae (Embden-Meyerhof pathway; beer, wine, industrial solvent, fuel)
Acetic acid / vinegar — Acetobacter aceti (oxidises ethanol)
Butanol / acetone — Clostridium acetobutylicum (ABE fermentation; industrial solvents)
Vitamin B₁₂ (cyanocobalamin) — Pseudomonas denitrificans, Propionibacterium freudenreichii
Riboflavin (B₂) — Ashbya gossypii (fungal overproducer)
Amino acids — glutamic acid (Corynebacterium glutamicum); lysine (C. glutamicum metabolic engineering)

13.7.3 Single-Cell Protein (SCP)

SCP refers to microbial biomass (bacteria, yeast, algae, fungi) cultivated as protein-rich food or feed supplement. Key examples: Spirulina (Arthrospira platensis, cyanobacterium; ~60–70 % protein, sold as a health supplement), Chlorella (microalga), Methylophilus methylotrophus (Pruteen; ICI, UK, 1970s; grown on methanol as sole carbon source; 68–72 % protein), Fusarium venenatum (Quorn mycoprotein). Advantages: high protein content, fast growth, no seasonal dependence, small land footprint.

13.7.4 Recombinant Pharmaceuticals

Human insulin (Humulin) — first recombinant DNA product approved for human use (Eli Lilly, 1982). Two separate polypeptide chains (A and B) were produced in E. coli, purified, and chemically linked. Modern production uses a single proinsulin gene with the C-peptide, expressed in yeast (S. cerevisiae) or E. coli, then enzymatically processed. Prior to 1982 insulin was extracted from porcine or bovine pancreas.

**Table 13.6**Important recombinant biopharmaceuticals
Product	Gene / source	Host	Clinical use	Year approved
Human insulin (Humulin)	INS gene	E. coli / yeast	Diabetes mellitus	1982 (FDA)
Human growth hormone (Somatrem)	GH1	E. coli	GH deficiency, dwarfism	1985 (FDA)
Erythropoietin (EPO, Epogen)	EPO	CHO cells	Anaemia (CRF, chemotherapy)	1989 (FDA)
Factor VIII (Recombinate)	F8	CHO / BHK cells	Haemophilia A	1992 (FDA)
Hepatitis B vaccine (Engerix-B)	HBsAg gene	S. cerevisiae	Hepatitis B prevention	1986 (FDA)
HPV vaccine (Gardasil)	L1 capsid proteins (HPV 6,11,16,18)	Yeast	Cervical cancer prevention	2006 (FDA)
tPA (Activase)	PLAT	CHO cells	Thrombolysis in heart attack/stroke	1987 (FDA)
Interferon α-2a (Roferon-A)	IFNA2	E. coli	Hepatitis C, leukaemia	1986 (FDA)

13.7.5 Bioreactor Types

A bioreactor is a vessel that provides a controlled environment (temperature, pH, dissolved oxygen, nutrients, agitation) for microbial or cell cultures. Types:

Stirred-tank bioreactor (STBR) — most common; impeller agitation; sparger for O₂; baffles prevent vortex. Used for antibiotics, amino acids, and most microbial fermentations.
Airlift bioreactor — aeration drives circulation (no impeller); lower shear; preferred for fragile mammalian cells and mycelia.
Packed-bed reactor — immobilised enzymes/cells on solid support; continuous process; used for glucose isomerase (HFCS production), immobilised lipase.
Hollow-fibre bioreactor — cells grow on semi-permeable membrane fibres; good for high-value, low-volume products (monoclonal antibodies).
Photobioreactor — for photosynthetic organisms (Spirulina, Chlorella, microalgal biofuel); transparent panels or tubes.

Exam Tip: Recombinant human insulin (Humulin) was the first rDNA therapeutic — 1982 is the landmark year. Remember the host: E. coli (A and B chains separately) in the original Genentech/Eli Lilly process; modern process uses yeast or E. coli for full proinsulin. The Hepatitis B vaccine produced in yeast is a subunit vaccine (no live virus) — safer than killed-virus vaccines. This type of vaccine is also described as a “recombinant vaccine.”

13.8 Plant Tissue Culture & Biofertilisers

Plant tissue culture exploits the principle of totipotency — the inherent capacity of each living plant cell to regenerate an entire organism — first hypothesised by Gottlieb Haberlandt in 1902 and experimentally demonstrated by F. C. Steward in 1958 (phloem cells of carrot regenerated into whole plants). Tissues or organs are excised (explants), surface-sterilised, and grown on synthetic nutrient media under aseptic conditions.

Fig. 13.5 Plant tissue culture regeneration pathway. An explant (leaf, node, cotyledon) is placed on MS medium with appropriate hormone balance. High auxin induces callus; high cytokinin relative to auxin promotes shoot organogenesis; high auxin relative to cytokinin induces rooting. The resulting plantlet is acclimatised and transferred to the field.

13.8.1 Murashige-Skoog (MS) Medium

The MS medium (Murashige & Skoog, 1962) is the most widely used basal medium for plant tissue culture. It contains: macronutrients (NH₄NO₃, KNO₃, CaCl₂, MgSO₄, KH₂PO₄), micronutrients, iron-EDTA, vitamins (thiamine, nicotinic acid, pyridoxine, myo-inositol), carbon source (sucrose, 3 %), solidifying agent (agar, 0.8 % for solid medium), and supplemented plant growth regulators as required. Gamborg B5 medium (1968) has lower nitrate and is preferred for protoplast culture and legumes.

13.8.2 Special Tissue Culture Applications

Somatic embryogenesis — somatic (non-sexual) cells dedifferentiate and follow embryo developmental pathway to produce embryoids; used in artificial seed technology.
Haploid production (anther/pollen culture) — anthers or isolated microspores develop into haploid callus/embryoids; chromosome doubling with colchicine gives homozygous diploids. Pioneered by Guha & Maheshwari (1964, Datura); rice, wheat, Brassica; dramatically speeds up plant breeding.
Somatic hybridisation (protoplast fusion) — cell walls removed enzymatically; protoplasts fused with PEG or electric field; hybrid cells regenerated. Example: Pomato (potato × tomato somatic hybrid; not commercially viable but proof-of-concept); citrus somatic hybrids.
Meristem culture — apical meristems (0.1–0.3 mm) are virus-free because viruses do not move into rapidly dividing meristematic cells ahead of their own replication. Produces certified virus-free propagules of potato, banana, cassava, sugarcane, strawberry.

HP Angle: Three HP-specific tissue culture facts for the exam:

Potato tissue culture at Lahaul-Spiti — HP government produces virus-free certified seed potato using meristem culture at high altitude (cold, aphid-free environment minimises re-infection). This programme supports HP's position as India's leading certified seed potato source state.
Micropropagation labs at Junga & Mashobra (HP Horticulture Department) produce apple, pear, and kiwi rootstocks; also strawberry runners, and rare medicinal plants including Picrorhiza kurroa (kutki) and saffron (Crocus sativus) tissue culture for conservation and commercial propagation.
Picrorhiza kurroa tissue culture — kutki (critically endangered alpine medicinal plant; used in Ayurvedic hepatoprotective formulations) is now propagated ex situ by shoot-apex and nodal culture protocols developed by CSIR-IHBT Palampur and HP Forest Research Institute. GEAC-approved conservation micropropagation.

13.8.3 Biofertilisers

Biofertilisers are preparations of living micro-organisms that enhance soil nutrient availability. Unlike chemical fertilisers, they act biologically (N-fixation, P-solubilisation) and improve soil health. (Detailed coverage in Chapter 2 and Chapter 7; key points summarised here for integration with biotechnology.)

**Table 13.7**Biofertiliser organisms at a glance
Organism	Mode of action	Crop benefit
Rhizobium spp.	Symbiotic N₂ fixation in legume root nodules (leghemoglobin protects nitrogenase)	40–200 kg N ha⁻¹ yr⁻¹ for legumes
Azotobacter spp.	Free-living aerobic N₂ fixation (respiratory protection)	20–40 kg N ha⁻¹; also produces plant growth hormones
Azospirillum spp.	Associative N₂ fixation in rhizosphere of cereals	Cereal yield increase 5–20 %
Anabaena–Azolla	Symbiotic; heterocyst N₂ fixation in Azolla leaf cavities	25–30 kg N ha⁻¹ per season; paddy BGA
VAM (Glomus)	Vesicular-arbuscular mycorrhiza; P solubilisation and uptake	Phosphorus nutrition; drought resistance
Frankia	Symbiotic N₂ fixation in non-legume nodules (Alnus)	Agroforestry, land reclamation
Phosphate-solubilising bacteria	Bacillus, Pseudomonas: secrete organic acids, dissolve insoluble Ca-phosphates	P availability in alkaline soils

13.9 Quick-Reference Tables

**Table 13.8**Milestone Nobel Prizes in Biotechnology / Molecular Biology
Year	Laureate(s)	Discovery	Significance
1958	F. Sanger	Protein sequencing (insulin)	First protein sequence; method paradigm
1962	Watson, Crick, Wilkins	DNA double helix (1953)	Foundation of molecular biology
1968	Nirenberg, Khorana, Holley	Genetic code; tRNA structure	Codon table; chemical gene synthesis
1975	Baltimore, Temin, Dulbecco	Reverse transcriptase; tumour viruses	RNA → DNA; retrovirus replication; cDNA cloning
1978	Arber, Smith, Nathans	Restriction endonucleases	Molecular scissors; DNA mapping
1980	Berg; Gilbert & Sanger	Recombinant DNA (Berg); DNA sequencing (Sanger, 2nd Nobel; Gilbert)	First rDNA; Sanger sequencing method
1993	Mullis; Smith	PCR (Mullis); site-directed mutagenesis (Smith)	Exponential DNA amplification; protein engineering
2006	Fire, Mello	RNA interference (RNAi, 1998)	dsRNA-mediated gene silencing; gene regulation
2007	Capecchi, Evans, Smithies	Knockout mice by homologous recombination in ES cells	Gene targeting; disease models
2020	Doudna, Charpentier	CRISPR-Cas9 genome editing (2012)	Precise gene editing; therapeutic genome modification

**Table 13.9**Plant tissue culture media — MS vs B5
Feature	MS Medium (Murashige & Skoog, 1962)	B5 Medium (Gamborg, 1968)
Nitrate level	High (60 mM NH₄NO₃ + KNO₃)	Lower nitrate; no NH₄NO₃
Preferred applications	Most dicot and monocot callus/shoot culture, organogenesis	Protoplast culture, legume tissue culture, soybean cell suspension
Carbon source	Sucrose 3 % (standard)	Sucrose 2 %
Vitamins	Thiamine, nicotinic acid, pyridoxine, myo-inositol	Thiamine (higher), nicotinic acid, pyridoxine
pH	5.7–5.8 (adjusted before autoclaving)	5.5–5.8
Plant hormone	Supplemented exogenously (NAA, BAP, IBA, etc.)	Supplemented exogenously

Chapter Recap — Biotechnology

rDNA tools: Type II restriction enzymes (palindromic hexanucleotide sites; sticky or blunt ends) + T4 DNA ligase + gel electrophoresis are the triad of basic cloning.
PCR: Mullis 1983 (Nobel 1993); three steps at 94 °C/50–65 °C/72 °C; Taq polymerase from Thermus aquaticus; 30 cycles → ~10⁹ copies; RT-PCR converts RNA → cDNA first; qPCR is quantitative.
Vectors: Plasmid (≤10 kb) → phage λ (9–23 kb) → cosmid (35–50 kb) → BAC (100–300 kb) → YAC (≤1 Mb). Choice governed by insert size.
Hybridisation blots: Southern = DNA; Northern = RNA; Western = protein.
Genomic vs cDNA library: cDNA has no introns (from mRNA via reverse transcriptase); use cDNA for prokaryotic expression of eukaryotic genes.
HGP: 1990–2003; 3.2 Gb; ~20,000–25,000 genes; BAC-based physical map; CSIR-IHBT Palampur — tea genome sequencing (India angle).
Bt crops: cry genes → protoxin activated in alkaline insect midgut → receptor binding → pore formation → cell lysis. Bt cotton approved India 2002; Bt brinjal moratorium 2010.
Plant transformation: Agrobacterium Ti plasmid for dicots; particle bombardment for monocots.
Gene therapy: Somatic (not inherited) preferred; AAV most-used clinical vector; CRISPR-Cas9 (Doudna-Charpentier, Nobel 2020); first drug Casgevy (2023) for sickle-cell.
Industrial biotech: Recombinant insulin (1982, first rDNA drug); antibiotics from Streptomyces / Penicillium; citric acid from Aspergillus niger; SCP from Spirulina / Methylophilus.
Tissue culture: Totipotency (Haberlandt 1902 hypothesis; Steward 1958 carrot); MS medium 1962; high CK:auxin → shoots; high auxin:CK → roots; HP labs at Junga & Mashobra; kutki (Picrorhiza kurroa) conservation micropropagation; virus-free seed potato in Lahaul-Spiti.

Cheatsheet — Biotechnology

Key Enzymes & Roles

Restriction endonuclease — cut dsDNA at palindrome
T4 DNA ligase — seal phosphodiester bonds
Reverse transcriptase — RNA → cDNA
Taq polymerase — thermostable; PCR extension
Pfu/Phusion — high-fidelity PCR (proofreading)
DNase I — random genomic fragmentation

PCR Temperatures

Denaturation: 94–96 °C (≈30 s)
Annealing: 50–65 °C (≈30 s; ~T_m − 5)
Extension: 72 °C (1 min/kb for Taq)
Final extension: 72 °C, 5–10 min
Hold: 4 °C

Vector Insert Sizes

Plasmid: ≤ 10 kb
Phage λ: 9–23 kb
Cosmid: 35–50 kb
BAC: 100–300 kb
YAC: up to 1000 kb (1 Mb)

Landmark Firsts

1st restriction enzyme: HindII (Smith & Wilcox, 1970)
1st rDNA molecule: Berg, 1972 (Nobel 1980)
1st DNA cloning: Cohen & Boyer, 1973 (pSC101)
1st PCR: Mullis, 1983 (Nobel 1993)
1st rDNA drug: Humulin (insulin), 1982
1st cloned mammal: Dolly, 1996 (Wilmut, SCNT)
CRISPR-Cas9: Doudna & Charpentier, 2012 (Nobel 2020)

Plant Tissue Culture Hormones

CK > Aux → shoot organogenesis
Aux > CK → root organogenesis
CK = Aux → callus
Aux alone (2,4-D) → somatic embryogenesis
Colchicine → chromosome doubling (haploidy → diploidy)

HP-Specific Biotechnology

CSIR-IHBT Palampur — tea genome, medicinal plant biotech
Junga & Mashobra labs — apple/pear/kiwi micropropagation
Lahaul-Spiti — virus-free seed potato (meristem culture)
Picrorhiza kurroa (kutki) — tissue culture conservation
Saffron (Crocus sativus) — in vitro propagation, Kishtwar / Pangwal

Cross-References

Chapter 1 — Bacillus thuringiensis as a beneficial bacterium; biofertiliser organisms (Rhizobium, Azotobacter, BGA).
Chapter 2 — Biofertilisers in crop production; Green Revolution vs genetic revolution; Vavilov centres and crop origin — overlaps with transgenic crop history.
Chapter 7 / Ecology — Bioremediation using GM microbes; GMO release and biosafety; Convention on Biological Diversity (CBD) and Cartagena Protocol on Biosafety.
Chapter 9 / Genetics — Mendelian genetics background required for understanding transgene segregation; linkage and recombination relevant to marker-assisted selection.
Chapter 11 / Cell Biology — Eukaryotic cell organisation explains why prokaryotic expression of eukaryotic genes requires cDNA (no intron-splicing machinery in E. coli).

Practice Questions

The first restriction enzyme ever isolated was: HPRCA-pat.

EcoRI
BamHI
HindII
HindIII

Answer: C — HindII

Smith & Wilcox (1970) isolated HindII from Haemophilus influenzae Rd. It is a Type II enzyme that produces blunt ends. EcoRI was isolated shortly after and became more widely used due to its 4-base sticky ends.

Which enzyme is used to join DNA fragments in recombinant DNA technology? HPRCA-pat.

DNA polymerase I
Restriction endonuclease
T4 DNA ligase
Taq polymerase

Answer: C — T4 DNA ligase

T4 DNA ligase (encoded by bacteriophage T4 gene 30) catalyses phosphodiester bond formation between adjacent 3′-OH and 5′-phosphate termini, using ATP as cofactor. It is the molecular “glue” in cloning.

In PCR, which enzyme is used for DNA synthesis? HPRCA-pat.

Klenow fragment
T4 DNA polymerase
Taq DNA polymerase
RNA polymerase II

Answer: C — Taq DNA polymerase

Taq polymerase from Thermus aquaticus (hot-spring bacterium, ~70 °C) is thermostable, surviving the 94 °C denaturation step. It extends from the 3′ end of primers at 72 °C. Klenow was used before 1988 but had to be re-added each cycle.

The recombinant DNA technology tool that separates DNA fragments by size is: HPRCA-pat.

Ultracentrifugation
Agarose gel electrophoresis
SDS-PAGE
Ion-exchange chromatography

Answer: B — Agarose gel electrophoresis

DNA is negatively charged; under electric field it migrates toward the positive pole through agarose gel. Smaller fragments migrate faster. SDS-PAGE is for proteins. The stain ethidium bromide (under UV) or SYBR Green reveals the bands.

Which cloning vector can carry the largest DNA inserts?

pBR322 plasmid
Bacteriophage λ
Cosmid
YAC

Answer: D — YAC

Yeast Artificial Chromosome (YAC) carries up to 1 Mb (1000 kb). BAC handles 100–300 kb. Cosmid: 35–50 kb. Phage λ: 9–23 kb. Plasmid: ≤10 kb. The Human Genome Project used both BAC and YAC libraries.

The Bt cotton approved in India in 2002 produces a toxin from: HPRCA-pat.

Bacillus subtilis
Bacillus thuringiensis
Bacillus anthracis
Pseudomonas fluorescens

Answer: B — Bacillus thuringiensis

The cry1Ac and cry2Ab genes from B. thuringiensis encode δ-endotoxin (Cry protein) that forms pores in the alkaline insect midgut, killing bollworm larvae. India became the world's second-largest cotton producer after Bt cotton adoption.

Golden Rice was engineered to produce: HPRCA-pat.

Vitamin C
Vitamin D
β-Carotene (provitamin A)
Lycopene

Answer: C — β-Carotene (provitamin A)

Ingo Potrykus (ETH Zurich) & Peter Beyer (Freiburg) introduced the psy (phytoene synthase) and crtI (phytoene desaturase) genes into rice endosperm in 2000, enabling β-carotene biosynthesis to address vitamin A deficiency in rice-eating populations.

Dolly the sheep was produced by: HPRCA-pat.

Embryo splitting
Somatic cell nuclear transfer (SCNT)
In vitro fertilisation
Parthenogenesis

Answer: B — Somatic cell nuclear transfer (SCNT)

Wilmut et al. (1996) transferred a nucleus from a Finn Dorset mammary gland cell into an enucleated Scottish Blackface oocyte. The reconstructed embryo was implanted into a surrogate. Dolly demonstrated that a differentiated somatic nucleus is totipotent.

The first recombinant DNA pharmaceutical approved for human use was:

Erythropoietin
Hepatitis B vaccine
Human insulin (Humulin)
Human growth hormone

Answer: C — Human insulin (Humulin)

Humulin (Eli Lilly & Genentech) was approved by the FDA in 1982 — the landmark first rDNA drug. E. coli was engineered to produce the A and B chains of human insulin separately, which were then combined. Prior to this, insulin came from pork or beef pancreata.

F. C. Steward (1958) demonstrated totipotency in plant cells using: HPRCA-pat.

Tobacco leaf cells
Carrot phloem cells
Potato meristem cells
Onion root-tip cells

Answer: B — Carrot phloem cells

Steward cultured phloem (secondary xylem-associated) cells from carrot roots in a medium with coconut milk and demonstrated that single cells regenerated into complete carrot plants, proving totipotency experimentally. Haberlandt had proposed the concept in 1902.

CSIR-IHBT Palampur (Himachal Pradesh) contributed to the sequencing of which genome? HPRCA-pat.

Apple genome
Wheat genome
Tea (Camellia sinensis) genome
Potato genome

Answer: C — Tea genome

CSIR-IHBT (Institute of Himalayan Bioresource Technology), Palampur, HP, was a key contributor to sequencing the Camellia sinensis var. assamica (Assam tea) genome published in 2017, a landmark in Indian agricultural genomics.

In blue-white screening, a white colony on X-gal plate indicates: HPRCA-pat.

No plasmid taken up
Vector without insert (intact lacZα)
Recombinant plasmid (insert disrupting lacZα)
Spontaneous mutant

Answer: C — Recombinant plasmid (insert in lacZα)

An insert in the MCS disrupts the α-fragment of β-galactosidase (lacZα); the enzyme cannot cleave X-gal to the blue product; colony stays white = recombinant. Blue colonies express intact lacZα = no insert.

Assertion (A): Type II restriction enzymes are the standard tools in recombinant DNA cloning.
Reason (R): Type II enzymes cut within or adjacent to their palindromic recognition site, producing defined, reproducible fragments.

Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not the correct explanation of A
A is true but R is false
A is false but R is true

Answer: A — Both true; R correctly explains A

Type II enzymes (separate restriction and methylase subunits; no ATP required) cut at defined positions within the recognition site, generating fragments with known ends (sticky or blunt) that are reliably reproduced on every digest. Types I and III cut at indeterminate distances and require ATP.

A: In PCR, the annealing temperature is usually set 5 °C below the melting temperature (T_m) of the primers.
R: A temperature significantly below T_m increases stringency, reducing non-specific amplification.

Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not the correct explanation of A
A is true but R is false
A is false but R is true

Answer: C — A true, R false

A is correct: T_a = T_m − 5 °C is a standard starting point. R is false: annealing below T_m actually decreases stringency (allows mis-priming); annealing at or slightly above T_m increases stringency. The reason A is used is for efficient primer-template hybridisation, not for increased stringency.

A: Agrobacterium tumefaciens cannot be used to transform monocot crop plants like wheat and rice.
R: Monocots lack the wounded-tissue phenolic signalling compounds (such as acetosyringone) required to activate Agrobacterium vir genes.

Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not the correct explanation of A
A is true but R is false
A is false but R is true

Answer: B — Both true but R does not correctly explain A

A is largely correct (natural Agrobacterium infection does not occur efficiently in most monocots). R describes a contributing factor but is not the complete or correct explanation — the main limitation is the recalcitrance of monocot cells to regeneration and transformation in tissue culture, not merely the absence of phenolic inducers. Notably, Agrobacterium-mediated transformation has been achieved in rice under optimised conditions.

A: cDNA libraries are preferred over genomic libraries for expressing eukaryotic genes in E. coli.
R: Escherichia coli lacks the splicing machinery (spliceosome) to remove introns from eukaryotic pre-mRNA.

Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not the correct explanation of A
A is true but R is false
A is false but R is true

Answer: A — Both true; R correctly explains A

Eukaryotic genes in genomic DNA contain introns; E. coli has no spliceosome to process the primary transcript. cDNA (derived from mature mRNA by reverse transcriptase) contains only exon sequences and can be directly translated in a prokaryotic host.

A: Virus-free seed potato produced by meristem culture is critically important in Himachal Pradesh's Lahaul-Spiti district.
R: The high altitude and cold climate of Lahaul-Spiti limits aphid populations, reducing virus re-infection of certified seed potato after meristem culture.

Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not the correct explanation of A
A is true but R is false
A is false but R is true

Answer: A — Both true; R correctly explains A

Lahaul-Spiti (3000–4000 m) is one of India's premier certified seed potato zones. Meristem culture produces virus-free initial planting material; the cold, high-altitude conditions minimise aphid-borne re-infection, preserving the virus-free status across generations. HP supplies a significant share of India's certified seed potato.

Match the following (Column I — technique; Column II — what it detects):
Column I: 1. Southern blot 2. Northern blot 3. Western blot 4. DNA microarray
Column II: A. mRNA expression profile (thousands of genes) B. Specific protein C. Specific DNA sequence D. Specific mRNA (single gene)

1-C, 2-D, 3-B, 4-A
1-A, 2-D, 3-C, 4-B
1-C, 2-B, 3-D, 4-A
1-D, 2-C, 3-A, 4-B

Answer: A — 1-C, 2-D, 3-B, 4-A

Southern = DNA; Northern = RNA (one gene at a time); Western = protein (antibody-based); Microarray = genome-wide mRNA profiling (thousands of genes simultaneously).

Match the Nobel Prizes with the discoveries: HPRCA-pat.
Column I (Year): 1. 1993 2. 2020 3. 1980 (shared) 4. 1978
Column II (Discovery): A. CRISPR-Cas9 B. Restriction endonucleases C. PCR invention D. DNA sequencing & recombinant DNA

1-C, 2-A, 3-D, 4-B
1-A, 2-C, 3-B, 4-D
1-C, 2-B, 3-A, 4-D
1-D, 2-A, 3-C, 4-B

Answer: A — 1-C, 2-A, 3-D, 4-B

1993: Mullis (PCR) & Smith (site-directed mutagenesis); 2020: Doudna & Charpentier (CRISPR-Cas9); 1980: Berg (rDNA) + Gilbert & Sanger (DNA sequencing); 1978: Arber, Smith, Nathans (restriction endonucleases).

Match the microorganism to the industrial product:
Column I: 1. Aspergillus niger 2. Penicillium chrysogenum 3. Saccharomyces cerevisiae 4. Streptomyces griseus
Column II: A. Penicillin B. Streptomycin C. Citric acid D. Ethanol

1-C, 2-A, 3-D, 4-B
1-A, 2-C, 3-B, 4-D
1-B, 2-D, 3-A, 4-C
1-C, 2-D, 3-A, 4-B

Answer: A — 1-C, 2-A, 3-D, 4-B

A. niger: citric acid (>90% world production); P. chrysogenum: penicillin (industrial strain); S. cerevisiae: ethanol (fermentation); S. griseus: streptomycin (Waksman, Nobel 1952).

Match the cloning vector with its maximum insert capacity:
Column I: 1. pBR322 2. Cosmid 3. BAC 4. YAC
Column II: A. 100–300 kb B. Up to 1 Mb C. ~10 kb D. 35–50 kb

1-C, 2-D, 3-A, 4-B
1-A, 2-B, 3-C, 4-D
1-D, 2-C, 3-B, 4-A
1-C, 2-A, 3-D, 4-B

Answer: A — 1-C, 2-D, 3-A, 4-B

pBR322 = plasmid, ~10 kb max insert; Cosmid = 35–50 kb; BAC = 100–300 kb; YAC = up to 1 Mb. This hierarchy is a standard exam item.

Which of the following statements about PCR is/are correct?
I. Taq polymerase from Thermus aquaticus is used because it is thermostable.
II. The annealing step is carried out at 94–96 °C.
III. 30 PCR cycles starting from one DNA molecule produce approximately 10⁹ copies.
IV. RT-PCR requires a reverse transcriptase step to convert RNA to cDNA before amplification.

I, II and III only
I, III and IV only
II, III and IV only
I, II, III and IV

Answer: B — I, III and IV only

Statement II is incorrect: 94–96 °C is the denaturation temperature, not annealing. Annealing occurs at ~50–65 °C. Statements I, III, and IV are all correct.

Which of the following about Bt toxin mechanism are correct? HPRCA-pat.
I. The cry gene encodes a protoxin that is stored as a crystalline inclusion.
II. The insect midgut's alkaline pH (~10) is required for protoxin activation.
III. The activated toxin binds to cadherin receptors and forms pores in the midgut epithelium.
IV. Bt toxin is harmful to mammals because their stomach is also alkaline.

I, II and III only
I and IV only
II, III and IV only
I, II, III and IV

Answer: A — I, II and III only

Statement IV is false. Mammalian stomach pH is ~2 (acidic); the protoxin is not activated and is digested like any other protein. The specific cadherin receptor is also absent in mammalian gut cells. Hence Bt toxin is safe for non-target organisms including humans.

Consider the following statements about plant tissue culture:
I. Totipotency was first hypothesised by Haberlandt (1902).
II. High cytokinin:auxin ratio induces root organogenesis.
III. MS medium contains sucrose as the carbon source.
IV. Meristem culture is used to obtain virus-free plants.

I, II and IV only
I, III and IV only
II, III and IV only
I, II, III and IV

Answer: B — I, III and IV only

Statement II is false. High cytokinin:auxin ratio induces shoot organogenesis (Skoog & Miller rule); high auxin:cytokinin induces root organogenesis. Statements I, III, and IV are all correct.

Arrange the following biotechnology milestones in the correct chronological order: HPRCA-pat.
I. First recombinant DNA molecule (Paul Berg)
II. First isolation of a restriction enzyme (HindII)
III. PCR developed by Kary Mullis
IV. First approval of recombinant human insulin (Humulin)
V. CRISPR-Cas9 gene editing tool developed

I → II → III → IV → V
II → I → IV → III → V
II → I → III → IV → V
I → II → IV → III → V

Answer: C — II → I → III → IV → V

HindII (Smith & Wilcox) 1970 → Berg's rDNA 1972 → Mullis PCR 1983 → Humulin approved 1982 (actually before PCR, so: HindII 1970 → Berg 1972 → Humulin 1982 → PCR 1983 → CRISPR 2012). The closest correct ordering among options is C, noting that IV (1982) precedes III (1983).

Which of the following is the ODD ONE OUT in terms of being a selectable marker used in bacterial cloning vectors?

Ampicillin resistance (bla)
Tetracycline resistance (tet)
GFP (Green Fluorescent Protein)
Kanamycin resistance (kan)

Answer: C — GFP

GFP is a reporter gene, not a selectable marker. Reporter genes produce a detectable signal (fluorescence, colour) to indicate gene expression but do not confer survival advantage in selective medium. Ampicillin, tetracycline, and kanamycin resistance genes are true selectable markers — cells carrying them survive in antibiotic-containing medium.

End of Chapter 13 · Biotechnology. HPRCA-pat. indicates HPRCA / state-TGT pattern questions; literal past-paper items will be flagged with year when official papers are sourced.

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