Biotechnology and its applications | ISC Class 12 Biology Notes

This note covers plant tissue culture, micropropagation, somatic hybridisation, genetically modified crops, insect resistance, gene silencing, human insulin, vaccine production, stem cells, gene therapy, molecular diagnosis, transgenic animals, biosafety, biopiracy and biopatents.

What does biotechnology contribute to agriculture and health?

Biotechnology uses living organisms, cells or their products to produce useful goods and processes. Its applications include medicines, disease detection, crop improvement, food processing, waste treatment and energy production. Modern applications include the industrial production of biological products using genetically modified organisms.

DNA, deoxyribonucleic acid, carries genetic information. A gene is a segment of genetic material with a functional product. Genetic engineering deliberately alters genetic material; recombinant DNA joins DNA from different sources. These ideas connect the production of a useful protein with the genetic instructions required to make it.

How does a useful biological product reach production?

Three central research areas support biotechnology. The first is obtaining a suitable catalyst, something that speeds a reaction, usually an improved microbe or a pure enzyme. An enzyme is a biological catalyst. The second is engineering suitable conditions for its activity.

The third is downstream processing, which includes separation and purification of the product. A useful organism alone does not complete a production system: its growth conditions and the recovery of the desired substance are also important.

How do the main applications differ?

In agriculture, biotechnology can change crop characteristics or rapidly multiply desirable plants. In medicine, it can produce human proteins, provide materials for vaccination, help detect disease or introduce a functional gene. These applications act at different stages, so production, diagnosis and treatment must be distinguished.

Therapeutics are products or approaches used to treat disease; diagnostics identify disease or its cause. Producing insulin is a therapeutic application. Detecting a disease-associated sequence of genetic material is a diagnostic application. Both use biological knowledge, but their immediate purposes differ.

How do tissue culture and micropropagation produce plants?

Definition: Plant tissue culture grows plant material under sterile conditions in a nutrient medium. An explant is the plant part removed for culture; totipotency is the capacity of a cell or explant to regenerate a whole plant.

Sterile conditions exclude contaminating microorganisms. The culture medium supplies nutrients needed by the growing material. It contains a carbon source such as sucrose, inorganic salts, vitamins, amino acids and growth regulators such as auxins and cytokinins, substances that influence plant growth and development.

What is micropropagation?

Micropropagation is the production of thousands of plants through tissue culture in a short time. The plants are genetically identical to the original plant and are called somaclones. Tomato, banana and apple are examples of food plants produced commercially using this method.

1. Take suitable plant material as an explant from the original plant.
2. Place it under sterile conditions in a medium containing the required nutrients and growth regulators.
3. Allow the cultured material to grow and regenerate whole plants through its totipotency.
4. Use tissue culture to multiply the selected plant rapidly, producing many genetically identical plants.

How can a diseased plant yield virus-free plants?

A meristem is a region of actively dividing plant cells. The apical meristem occurs at a growing tip, while an axillary meristem is associated with an axillary bud. Even in a virus-infected plant, the apical and axillary meristems are free of virus.

Removing and culturing the meristem in vitro, meaning outside the organism under laboratory conditions, can therefore produce virus-free plants. Meristems of banana, sugarcane and potato have been cultured successfully. The selected starting tissue matters as much as the ability to multiply it.

Note: Micropropagation multiplies selected plant material. The production of genetically identical plants should not be confused with introducing a new foreign gene into them.

How does somatic hybridisation differ from micropropagation?

A protoplast is a plant cell whose cell wall has been removed, leaving its contents enclosed by the plasma membrane. The plasma membrane is the boundary surrounding the cell contents. Digesting the walls of isolated plant cells makes their protoplasts available for fusion.

Somatic hybridisation joins protoplasts from different plant varieties to obtain a hybrid plant. Here, somatic refers to body cells rather than reproductive cells. Each starting variety may possess a desirable character that the breeder wishes to combine with another.

What are the main steps?

1. Isolate cells from two plant varieties selected for their desirable characteristics.
2. Digest their cell walls to obtain naked protoplasts surrounded by plasma membranes.
3. Fuse protoplasts from the different varieties to obtain hybrid protoplasts.
4. Grow the hybrid protoplasts further to regenerate new plants called somatic hybrids.

Fusion of tomato and potato protoplasts produced pomato. However, this plant did not have all the desired combinations of characteristics for commercial use. Creating a hybrid is therefore distinct from obtaining a commercially useful combination of traits.

What is being copied or combined?

Both methods depend on growing plant material in culture. Their outcomes differ because one multiplies the selected material, whereas the other begins by combining protoplasts. Neither name, by itself, means that a particular insect-resistance gene has been introduced.

Why are genetically modified crops developed?

Genetically modified organisms, abbreviated GMOs, are plants, animals, fungi or bacteria whose genes have been altered by manipulation. GM means genetically modified. Genetic modification can provide a crop with a chosen characteristic, but different modifications serve different purposes.

Which agricultural problems can modification address?

Abiotic stresses arise from non-living environmental conditions. Genetic modification has made crops more tolerant to cold, drought, salt and heat. Tolerance means an improved ability to withstand the stress; it should not be described as complete independence from suitable growing conditions.

• Pest resistance reduces reliance on chemical pesticides by protecting crops against targeted pests.
• Reduced post-harvest losses help preserve produce after it has been harvested.
• Efficient mineral use helps prevent early exhaustion of soil fertility.
• Improved nutritional value changes the food value of a crop, as illustrated by golden rice, vitamin A-enriched rice.

Genetic modification can also produce plants supplying industrial resources such as starches, fuels and pharmaceuticals, substances used as medicines. Thus, the objective may concern crop survival, the use of resources, the quality of food or the product obtained from the plant.

How should benefits be interpreted?

Agrochemical-based agriculture, organic agriculture and genetically engineered crop-based agriculture are approaches to food production. Agrochemicals include fertilisers and pesticides; they are often too expensive for farmers in the developing world. Improved varieties alone do not explain increased yields, because management practices also contribute.

GM crops are a possible solution to some agricultural problems. Pest-resistant plants could decrease pesticide use. These statements do not establish that every modified crop has every listed benefit, or that all pesticides become unnecessary. The chosen gene, crop and targeted problem must be linked.

How does Bt cotton resist insect attack?

Bt abbreviates Bacillus thuringiensis, a bacterium. Some strains produce proteins that kill certain insects. A strain is a variant within a microbial species. Bt toxin genes can be introduced into crops so that the plants produce insecticidal proteins.

The affected insect groups include lepidopterans such as tobacco budworm and armyworm, coleopterans such as beetles, and dipterans such as flies and mosquitoes. These names identify groups of insects; they do not mean that one Bt protein kills every insect.

Why does the toxin become active in the insect?

The bacterium forms protein crystals during a particular growth phase. The toxin occurs as an inactive protoxin, a precursor requiring activation. This explains why the crystals do not kill the bacterium producing them.

1. An insect ingests the inactive Bt toxin contained in the protein crystals.
2. The alkaline conditions of its gut dissolve the crystals and convert the toxin into an active form. Alkaline means having a pH above neutral; pH measures acidity or alkalinity.
3. The active toxin binds to epithelial cells lining the midgut, the middle region of the digestive tract.
4. Pores form in the cells, causing swelling and lysis, meaning cell rupture, and eventually the insect dies.

Which genes protect which crops?

cry identifies genes encoding Bt toxin proteins. The proteins encoded by cryIAc and cryIIAb control cotton bollworms, while the protein encoded by cryIAb controls corn borer. The gene names are identifiers, not quantities or mathematical symbols.

Gene selection depends on the crop and targeted pest because most Bt toxins are insect-group specific. The gene supplies instructions; the resulting protein produces the toxic effect after activation. Keeping gene and protein distinct makes the mechanism clearer.

This photograph shows cotton bolls on stems held in a hand. Label (a) identifies bollworm-damaged material; label (b) identifies a mature boll with exposed white cotton. It shows contrasting outcomes, not the cellular action of the toxin.

See Fig. 10.1 in your NCERT textbook

How does RNA interference protect tobacco from nematodes?

RNA, ribonucleic acid, participates in the use of genetic information. Messenger RNA, abbreviated mRNA, carries information used to make a protein. Translation is the process of producing a protein using that message. Preventing translation can silence the expression of a gene.

RNA interference, or RNAi, silences a specific mRNA through a complementary double-stranded RNA molecule. Complementary sequences can pair through matching bases. Double-stranded RNA, abbreviated dsRNA, contains two paired RNA strands. RNAi occurs in all eukaryotic organisms, whose cells have a membrane-bound nucleus, as a cellular defence mechanism.

How is the protective RNA produced?

Meloidogyne incognita is a nematode, a roundworm, that infects tobacco roots and greatly reduces yield. Agrobacterium, a bacterium used for transferring genes into plants, supplies a vector, a carrier that delivers genetic material into a host cell.

1. Use Agrobacterium vectors to introduce nematode-specific genes into the tobacco plant.
2. Arrange the introduced DNA to produce both sense and antisense RNA. These terms identify the two complementary RNA sequences.
3. Allow the complementary RNAs to form dsRNA, initiating RNA interference.
4. Silence the specific nematode mRNA, preventing its translation. The parasite cannot survive in the transgenic host expressing the interfering RNA.

A transgenic plant contains an introduced foreign gene. Here its protection depends on interfering RNA, rather than on an insecticidal protein. Bt action and RNAi therefore illustrate different ways in which genetic manipulation can protect a crop.

Panel (a) shows control roots with conspicuous swellings and an enlarged inset. Panel (b) shows a finer root network from a protected transgenic plant, photographed five days after deliberate nematode infection. These are photographs of roots, not drawings of RNA molecules.

See Fig. 10.2 in your NCERT textbook

How is human insulin produced using genetic engineering?

Insulin is a hormone involved in regulating blood glucose, the sugar circulating in blood. A hormone is a chemical messenger. Insulin used to manage diabetes was earlier obtained from the pancreases of slaughtered cattle and pigs. Some patients developed allergies or other reactions to the foreign protein.

Human insulin contains two short polypeptide chains, chains of amino acids, called A and B. Disulphide bridges, bonds involving sulphur atoms, connect the chains. A and B are names identifying the two components, not algebraic variables.

Why does insulin need processing?

In mammals, including humans, insulin is first synthesised as proinsulin, an immature pro-hormone that requires processing to become functional. It contains an additional segment called the C peptide. This segment is removed during maturation and is absent from mature insulin.

The simplified drawing shows proinsulin above an arrow. Below it, the A peptide and B peptide remain joined by sulphur links as insulin, while a separate curved segment is labelled free C peptide.

See Fig. 10.3 in your NCERT textbook

How were the two chains manufactured?

In 1983, Eli Lilly prepared separate DNA sequences corresponding to the A and B chains. The sequences were introduced into plasmids, independently replicating DNA molecules used as carriers, in the bacterium Escherichia coli, abbreviated E. coli.

1. Prepare the DNA sequences coding for the A and B chains of human insulin.
2. Introduce these sequences into bacterial plasmids so that the bacteria produce the chains separately.
3. Extract the separately produced A and B chains from the production system.
4. Combine the chains by forming disulphide bonds to produce human insulin.

The central production challenge was obtaining insulin in its mature form. The separate-chain method must be distinguished from the natural removal of C peptide from proinsulin. Both descriptions end with mature insulin, but they describe different routes to that product.

How does biotechnology support vaccine production and stem-cell technology?

A vaccine is a preparation of antigenic proteins or weakened or inactivated disease-causing organisms that stimulates protective immune responses. An antigen is a substance recognised by the immune system; an antibody is an immune protein that binds a corresponding antigen. A pathogen is a disease-causing organism or agent.

How are recombinant vaccines made useful?

Recombinant DNA technology allows bacteria or yeast to produce antigenic polypeptides from a pathogen. This supports large-scale vaccine production and greater availability for immunisation, the development of protection against disease. Hepatitis B vaccine, produced using yeast, is an example.

Vaccination uses the immune system's memory. It generates memory B and T cells, immune cells that recognise the pathogen on later exposure and support a rapid response. Producing the antigen in a microbe and developing immune memory in the recipient are distinct parts of the application.

What are stem cells and what can they do?

Stem cells are unspecialised cells that can renew themselves and give rise to specialised cells. Differentiation is the development of specialised cell features and functions. The inner cell mass, the group of cells that forms the embryo, contains stem cells capable of giving rise to all body tissues and organs.

Stem-cell technology uses these properties to study cell development and generate cells for research or treatment. Blood-forming stem cells in bone marrow can restore blood-cell formation through transplantation. Bone marrow is the soft tissue inside bones where blood cells are formed.

Producing replacement cells for damaged tissues is an important aim of regenerative medicine, medicine directed towards restoring damaged cells or tissues. This potential should not be confused with an established cure for every disease. A cell's capacity to differentiate and the success of a treatment are separate questions.

How can gene therapy address ADA-deficient SCID?

Gene therapy introduces genes into a person's cells or tissues to treat disease. A normal functional gene can compensate for a non-functional gene. SCID means severe combined immunodeficiency, a condition in which major parts of the immune response are severely impaired.

Deficiency of adenosine deaminase, abbreviated ADA, is one cause of SCID. ADA is an enzyme crucial for immune-system function. The example considered here involves deletion of the ADA gene. It must not be generalised to mean that every case of SCID has this cause.

What happens during the lymphocyte treatment?

The first clinical gene therapy was given in 1990 to a four-year-old girl with ADA deficiency. Lymphocytes are white blood cells involved in immune responses. A retroviral vector is a modified retrovirus used to deliver genetic material into cells.

1. Remove lymphocytes from the patient's blood and grow them in culture outside the body.
2. Introduce functional ADA complementary DNA, or cDNA, using a retroviral vector. Complementary DNA is DNA made using an RNA template.
3. Return the genetically modified lymphocytes to the patient so that they can provide the missing enzyme function.
4. Repeat the infusion periodically because these lymphocytes are not immortal and do not provide a permanent population of corrected cells.

What is the limitation of this approach?

In some children, ADA deficiency can be cured by bone marrow transplantation; enzyme replacement supplies functional ADA by injection. These approaches are not completely curative. Lymphocyte gene therapy also has the stated limitation of requiring periodic infusions.

If a gene isolated from marrow cells producing ADA were introduced into cells at early embryonic stages, it could be a permanent cure. The word “could” matters: this is a conditional possibility, not a claim that periodic lymphocyte treatment permanently cures the disorder.

How do PCR, ELISA and probes help diagnose disease?

Molecular diagnosis detects disease through molecules associated with a pathogen or a genetic change. Early detection matters because symptoms may appear only when the pathogen concentration is already high. Molecular techniques can identify very small amounts of relevant material before visible symptoms develop.

How does amplification help detection?

Polymerase chain reaction, abbreviated PCR, makes many copies of a selected DNA segment in vitro. Amplification means increasing the number of copies. It helps detect low amounts of genetic material associated with bacteria or viruses and can identify changes in genes.

PCR uses primers, short DNA sequences complementary to regions of the target, and DNA polymerase, the enzyme that builds DNA. Repeated cycles separate the DNA strands, allow primers to bind, and extend them. These steps are called denaturation, annealing and extension, respectively.

What do ELISA and probes recognise?

Enzyme-linked immunosorbent assay, abbreviated ELISA, relies on antigen-antibody interaction. Infection may be detected through pathogen antigens or through antibodies made against the pathogen. The recognition principle is distinct from copying nucleic acid, the class of molecules comprising DNA and RNA.

A probe is labelled single-stranded DNA or RNA that pairs with a complementary sequence. Hybridisation means pairing complementary nucleic-acid strands. A radioactively labelled probe can be detected by autoradiography, recording radiation on photographic film.

In the described normal-sequence probe example, a mutation, a change in genetic sequence, removes the required complementarity. The clone carrying the mutated gene does not appear on the film. A clone is a group of cells derived from a common original cell.

Why are transgenic animals produced?

Transgenic animals have their DNA manipulated so that they possess and express an extra foreign gene. Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced. Their uses include studying gene function, modelling diseases, producing biological products and testing safety.

How do they support research and production?

Changing gene expression allows researchers to study normal body functions and development. Gene expression is the use of genetic information to produce its functional product. Transgenic animals can also serve as disease models, organisms used to investigate disease mechanisms and possible treatments.

They can produce useful biological substances. Alpha-1-antitrypsin, a human protein used in treating emphysema, illustrates this application. Emphysema is a lung disorder involving damage to air-sac walls and reduced respiratory surface. The name alpha-1-antitrypsin identifies the protein; “alpha” is not a numerical variable.

In 1997, the transgenic cow Rosie produced human protein-enriched milk containing alpha-lactalbumin, a milk protein. The reported human protein concentration was 2.4 grams per litre. The milk was nutritionally more balanced for human babies than natural cow's milk.

What are the safety-testing applications?

Transgenic mice are being developed for vaccine safety testing and are used to test polio vaccine safety. If successful and found reliable, they could replace monkeys in testing the safety of vaccine batches. This conditional claim does not mean replacement has already been completed.

In toxicity testing, the study of harmful effects of substances, animals carry genes that make them more sensitive to toxic substances than non-transgenic animals. Researchers expose them to the substance and study its effects. This will provide results in less time.

Producing a medicine and testing its safety are different uses of transgenic animals. A protein-producing animal supplies a product; a test animal helps reveal biological effects. Neither application removes the need to consider the ethical consequences of manipulating living organisms.

Why do biosafety, biopatents and biopiracy require attention?

Biosafety concerns assessing and managing potential biological risks to living organisms and the environment. Introducing genetically modified organisms into an ecosystem can have unpredictable results. An ecosystem comprises organisms and their physical environment interacting together. A useful trait therefore does not by itself establish safe release.

GEAC, the Genetic Engineering Approval Committee, makes decisions concerning the validity of GM research and the safety of introducing GM organisms for public services. Regulation considers biological consequences as well as the purposes for which organisms are modified.

How does a biopatent differ from biopiracy?

A biopatent is a patent relating to a biological invention, product or process. A patent grants legal rights over an invention for a limited period. Biopiracy is the use of biological resources by companies or other organisations without proper authorisation from the countries and people concerned and without compensatory payment.

A patent and biopiracy are therefore not synonyms. The ethical issue arises when claims to an invention exploit biological resources or traditional knowledge already developed and used by communities without appropriate authorisation and benefit sharing.

What do the Basmati and turmeric examples show?

In 1997, an American company obtained patent rights on Basmati rice through the United States Patent and Trademark Office. Its claimed new variety had been derived from Indian farmers' varieties by crossing Indian Basmati with semi-dwarf varieties, plants of relatively short stature.

Attempts have also been made to patent uses, products and processes based on traditional Indian herbal medicines such as turmeric. This illustrates the concern that existing knowledge may be claimed commercially without recognising those who developed and maintained it.

Benefit sharing concerns distributing benefits from the use of biological resources and associated knowledge. Ethical evaluation asks who might benefit or be harmed, whether communities have authorised use, and whether they receive compensation. Biological safety and fairness to resource-holding communities are related but distinct concerns.

Glossary

• Explant — A part of a plant removed and grown in a nutrient medium under sterile conditions.
• Totipotency — The capacity of a plant cell or explant to regenerate into a whole plant.
• Micropropagation — Rapid production of large numbers of plants through tissue culture from selected plant material.
• Somaclones — Plants produced through tissue culture that are genetically identical to the original plant.
• Protoplast — A plant cell without its cell wall, with its contents enclosed by the plasma membrane.
• Somatic hybridisation — Fusion of protoplasts from different plant varieties followed by regeneration of hybrid plants.
• Protoxin — An inactive toxin precursor that must undergo activation before exerting its toxic effect.
• RNA interference — Silencing of a specific messenger RNA through complementary double-stranded RNA, preventing translation of the message.
• C peptide — The extra segment removed from proinsulin during maturation and absent from mature insulin.
• Stem cells — Unspecialised cells capable of self-renewal and of developing into specialised cell types.
• Gene therapy — Introduction of genes into a person's cells or tissues to treat a disease.
• Probe — Labelled single-stranded DNA or RNA used to identify a complementary nucleic-acid sequence.
• Transgenic animal — An animal whose DNA has been manipulated to possess and express an extra foreign gene.
• Biopatent — A patent relating to a biological invention, product or process, conferring legal rights for a limited period.
• Biopiracy — Use of biological resources without proper authorisation from the countries and people concerned and without compensatory payment.

Common errors and misconceptions

• Misconception: Micropropagation necessarily introduces a foreign gene. Correct: It rapidly multiplies plants through tissue culture, producing genetically identical somaclones from selected material.
• Misconception: Pomato proves that every somatic hybrid is commercially successful. Correct: Pomato did not combine all the desired characteristics for commercial use.
• Misconception: Bt toxin is active inside the bacterium. Correct: It occurs as an inactive protoxin and is activated under alkaline conditions in the insect gut.
• Misconception: Bt crops and RNAi-protected tobacco work through the same toxin. Correct: Bt uses an insecticidal protein; RNAi silences a specific nematode mRNA.
• Misconception: Mature insulin retains the C peptide. Correct: The C peptide is removed during maturation, leaving the A and B chains connected by disulphide bridges.
• Misconception: ADA gene therapy using lymphocytes needs just one infusion. Correct: Periodic infusions are required because the modified lymphocytes are not immortal.
• Misconception: Stem-cell potential establishes a cure for every damaged tissue. Correct: Differentiation potential and successful clinical treatment are different matters.
• Misconception: Every biopatent is biopiracy. Correct: Biopiracy involves unauthorised exploitation without compensatory payment; a biopatent is a legal right concerning a biological invention.

Exam-style questions with model answers

Q1. An apical meristem from a virus-infected banana plant is free of virus. It is cultured under sterile conditions and regenerates whole plants. Explain the health of the regenerated plants and name the regenerative capacity involved. [2 marks]

1. The regenerated plants can be virus-free because the starting meristem is free of virus, despite infection elsewhere in the parent plant.
2. The regenerative capacity is totipotency: the ability of a plant cell or explant to produce a whole plant.

Q2. Tomato and potato cells have their walls removed; their protoplasts are fused and grown into pomato plants. These plants lack all the desired characteristics for commercial use. Identify the technique, explain the role of protoplasts and assess the outcome. [3 marks]

1. The technique is somatic hybridisation because it combines protoplasts from different plants and regenerates a hybrid plant, rather than simply multiplying one selected original plant.
2. Removing the cell walls makes membrane-bound protoplasts available for fusion. The fused material can then be grown to produce somatic hybrids.
3. The resulting pomato demonstrates successful hybrid formation, but not commercial success, because it lacks the full desired combination of characteristics.

Q3. An insect ingests inactive Bt protein crystals. Its gut is alkaline, and the activated toxin binds to midgut epithelial cells. Explain the sequence leading to insect death in four stages. [4 marks]

1. The ingested protein initially occurs as an inactive protoxin within the crystals, so ingestion precedes the activation necessary for its toxic action.
2. The alkaline gut conditions dissolve the crystals and convert the inactive protoxin into its active toxin form.
3. The activated toxin binds to the surface of midgut epithelial cells and produces pores in those cells.
4. The affected cells swell and undergo lysis, meaning rupture, and this cellular damage eventually causes the insect's death.

Q4. Nematode-specific DNA is introduced into tobacco using an Agrobacterium vector. The DNA produces complementary sense and antisense RNA; the parasite cannot survive in plants expressing the interfering RNA. Explain the protective mechanism in five points. [5 marks]

1. The Agrobacterium vector delivers nematode-specific genetic material into the tobacco host, enabling the plant to produce RNA associated with the parasite's genes.
2. The introduced DNA produces both sense and antisense RNA in the host cells. Their complementary sequences allow the two RNA molecules to pair.
3. Pairing forms double-stranded RNA, abbreviated dsRNA. This molecule initiates RNA interference, the cellular mechanism responsible for silencing the relevant message.
4. RNA interference silences the specific nematode messenger RNA and prevents its translation, so the message cannot direct production of its protein.
5. The parasite cannot survive in the transgenic host expressing the interfering RNA. The plant is consequently protected through gene silencing.

Q5. A patient has ADA deficiency. Blood lymphocytes are cultured, functional ADA cDNA is delivered using a retroviral vector, and the cells are returned to the patient. The cells are not immortal. Explain the treatment and its limitation in five points. [5 marks]

1. The treatment is gene therapy, which introduces genetic material into the patient's cells to compensate for a defective gene and supply a missing function.
2. The patient's blood lymphocytes are grown outside the body, providing a population of cells into which the functional genetic material can be introduced.
3. A retroviral vector delivers functional ADA cDNA into these lymphocytes, enabling the modified cells to provide adenosine deaminase enzyme function.
4. The genetically modified lymphocytes are returned to the patient. They carry the introduced functional sequence, rather than receiving only an injection of enzyme.
5. Periodic infusions are required because the modified lymphocytes are not immortal. The described treatment therefore does not establish a permanent corrected-cell population.

Q6. A human-insulin production system makes the A and B chains separately in E. coli using DNA carried by plasmids. The chains are extracted and joined by disulphide bonds. Explain the roles of the DNA sequences, bacteria and final assembly. [3 marks]

1. The DNA sequences code for the human insulin A and B chains. The plasmids carry these instructions into the bacterial production system.
2. The E. coli cells produce the two polypeptide chains separately, allowing the chains to be obtained from the production system by extraction.
3. Final assembly joins the extracted chains through disulphide bonds, yielding human insulin with its two chains connected in the mature molecule.

Q7. A sample contains very little pathogen DNA. A second test detects antibodies against that pathogen. Separately, a labelled normal-sequence DNA probe fails to pair with a mutated gene because complementarity is absent. Identify the first two diagnostic methods and explain the probe result and detection principle. [4 marks]

1. PCR can detect the low amount of pathogen DNA by amplifying a selected target sequence, making many copies from the small starting quantity.
2. ELISA detects the antibodies through specific antigen-antibody interaction, providing evidence of the immune response to the pathogen.
3. The labelled probe depends on complementary sequence pairing, called hybridisation, to recognise and bind its matching genetic sequence.
4. The mutated gene lacks the required complementarity, so the probe does not hybridise; this target therefore lacks the expected probe signal.

Q8. An organisation uses a community's biological resources and traditional knowledge without proper authorisation or compensatory payment, then seeks a patent on a resulting biological product. Identify the exploitation and distinguish it from a biopatent. [2 marks]

1. The unauthorised use without compensatory payment is biopiracy, because the resource-holding community's authorisation and compensation are absent.
2. A biopatent is a patent concerning a biological invention, product or process; it is distinct from the exploitative conduct described.

Key takeaways

• Micropropagation rapidly multiplies selected plants through tissue culture, while meristem culture can recover virus-free plants from infected parents.
• Somatic hybridisation fuses protoplasts from different varieties; obtaining a hybrid does not ensure commercial usefulness.
• Most Bt toxins are insect-group specific, and their inactive protoxins become active in the alkaline insect gut.
• RNA interference protects tobacco by silencing a specific nematode mRNA through complementary double-stranded RNA.
• Mature insulin contains A and B chains joined by disulphide bridges and lacks the C peptide of proinsulin.
• Gene therapy using modified lymphocytes requires periodic infusions because the treated cells are not immortal.
• PCR amplifies DNA, ELISA uses antigen-antibody interaction, and probes identify complementary nucleic-acid sequences through hybridisation.
• Transgenic applications require attention to biological safety, ethical consequences, authorisation for resource use and fair benefit sharing.

Test yourself

What makes an explant different from a protoplast?

An explant is plant material taken for culture. A protoplast is a cell whose wall has been removed, leaving a plasma-membrane boundary.

Why does inactive Bt toxin not kill the bacterium producing it?

It occurs as an inactive protoxin. Activation takes place after ingestion under alkaline conditions in the insect gut.

Which Bt genes are associated with cotton bollworms and corn borer?

Proteins encoded by cryIAc and cryIIAb control cotton bollworms; the protein encoded by cryIAb controls corn borer.

What forms when complementary sense and antisense RNA pair?

They form double-stranded RNA, which initiates RNA interference and silences the specific messenger RNA.

What happens to the C peptide during insulin maturation?

The C peptide is removed from proinsulin and is absent from the mature insulin molecule.

Which organism is used to produce the recombinant hepatitis B vaccine example?

Yeast is used to produce the antigenic material for the recombinant hepatitis B vaccine.

Why is periodic infusion needed in lymphocyte-based ADA gene therapy?

The genetically modified lymphocytes are not immortal, so the patient requires repeated supplies of those cells.

What two omissions characterise biopiracy?

It lacks proper authorisation from the countries and people concerned and lacks compensatory payment for use of their biological resources.