101. Match each natural situation with its relation to RNA interference.
| Situation | Relation |
|---|
| P. Infection by an RNA-genome virus | I. Can provide complementary RNA involved in a silencing response |
| Q. Mobile genetic element replicating through an RNA intermediate | II. Can generate RNA capable of participating in sequence-specific silencing |
| R. Bt crystal protein | III. Belongs to a protein-toxin mechanism rather than the natural RNA source examples |
| S. Plant protoplast fusion | IV. Belongs to somatic hybridisation rather than RNAi initiation |
ⓐ. P-II, Q-I, R-IV, S-III
ⓑ. P-III, Q-IV, R-I, S-II
ⓒ. P-I, Q-II, R-III, S-IV
ⓓ. P-IV, Q-III, R-II, S-I
Correct Answer: P-I, Q-II, R-III, S-IV
Explanation: RNA interference can arise naturally when complementary RNA is produced during processes such as infection by an RNA-genome virus or activity of mobile genetic elements that replicate through an RNA intermediate. These sources can create RNA relationships that trigger sequence-specific silencing. Bt crystal protein represents a different pest-control principle based on an insecticidal protein rather than complementary RNA, while protoplast fusion belongs to somatic hybridisation. The matching highlights that RNAi is not an artificial mechanism invented only for crop engineering. Biotechnology exploits an existing cellular defence principle by arranging for a host plant to produce RNA corresponding to a selected parasite gene. Successful transformation is only the first step; the introduced construct must generate the complementary RNA needed to silence the nematode target. Sense and antisense transcripts can generate double-stranded RNA, which provides the molecular basis for target-mRNA silencing.
102. A researcher wishes to protect tobacco from Meloidogyne incognita through RNA interference. Nematode-specific DNA sequences are introduced into tobacco cells using Agrobacterium. The primary role of Agrobacterium in this strategy is to:
ⓐ. deliver the selected nematode-related genetic sequences into the plant
ⓑ. act as the parasitic nematode whose gene must be silenced
ⓒ. produce Bt toxin crystals inside tobacco roots
ⓓ. digest the plant cell wall to create somatic hybrids
Correct Answer: deliver the selected nematode-related genetic sequences into the plant
Explanation: Agrobacterium serves as a vector for transferring the selected nematode-specific genetic sequences into tobacco cells. Once those sequences are present and expressed appropriately, the plant can produce complementary sense and antisense RNAs that form double-stranded RNA associated with the RNAi response. The bacterium is part of the gene-delivery step, not the target parasite. Meloidogyne incognita is the nematode whose gene expression is to be suppressed. Bt toxin production and protoplast formation belong to different biotechnology mechanisms. The role of the vector is crucial since it establishes the transgenic host capable of generating the RNA molecules needed for sequence-specific interference with nematode gene expression. The protective phenotype follows from sequence-specific inhibition of target-mRNA expression, which can prevent the nematode from surviving normally in the engineered host.
103. Use the arrangement described below. Nematode-specific sequences are introduced into tobacco. Transcript P is produced from one orientation and Transcript Q from the complementary orientation. P and Q pair with one another before the parasite's target mRNA is silenced. The molecular product formed by pairing P and Q is:
ⓐ. a Bt protein crystal
ⓑ. a somatic hybrid nucleus
ⓒ. a mature insulin molecule
ⓓ. complementary double-stranded RNA
Correct Answer: complementary double-stranded RNA
Explanation: Transcription of the introduced sequences in opposite orientations produces sense and antisense RNAs with complementary nucleotide sequences. When these transcripts pair, they form double-stranded RNA. This dsRNA is central to the sequence-specific RNA interference mechanism and provides the basis for targeting the corresponding nematode mRNA. The product is a nucleic-acid structure, not an insecticidal protein, a hybrid plant-cell nucleus or a therapeutic peptide. In the engineered tobacco system, formation of complementary dsRNA links transgene expression in the host with suppression of gene expression in the parasite. That molecular bridge is what allows the plant to interfere specifically with a nematode gene required for successful survival. RNAi and Bt can both provide pest resistance, but RNAi acts through target-mRNA silencing rather than through an insecticidal pore-forming protein.
104. A tobacco transformation produces the intended nematode-specific sense RNA but fails to produce the complementary antisense RNA. No alternative source of the matching complementary strand is present. The most likely effect is:
ⓐ. enhanced formation of the intended double-stranded RNA
ⓑ. reduced formation of dsRNA and weaker sequence-specific silencing
ⓒ. activation of Bt protoxin in the tobacco root
ⓓ. automatic production of a second complementary transcript by the nematode
Correct Answer: reduced formation of dsRNA and weaker sequence-specific silencing
Explanation: The engineered strategy depends on production of complementary sense and antisense transcripts that can pair to form double-stranded RNA. If only the sense transcript is produced and no matching complementary strand is available, formation of the intended dsRNA is impaired. Since dsRNA provides the sequence-specific trigger for silencing the corresponding nematode mRNA, the downstream RNAi effect would also be weakened. This prediction follows from the dependency between transcript complementarity and formation of the silencing molecule. The defect does not activate the Bt mechanism, and the nematode cannot simply be assumed to supply the missing engineered transcript. The changed condition interrupts the pathway before effective target-mRNA suppression is established. Changing the target sequence can alter silencing efficiency if the complementary relationship needed for recognition is disrupted.
105. Examine the statements below about the engineered tobacco RNAi system.
I. Sense and antisense RNAs are produced from nematode-specific introduced sequences.
II. The complementary transcripts can pair to form double-stranded RNA.
III. The resulting RNAi response can suppress the corresponding nematode mRNA.
IV. Agrobacterium is the root-parasitic nematode killed by the RNAi response.
Which combination is valid?
ⓐ. I, II and III only
ⓑ. I and IV only
ⓒ. II, III and IV only
ⓓ. I, III and IV only
Correct Answer: I, II and III only
Explanation: The engineered tobacco strategy introduces nematode-specific sequences so that complementary sense and antisense RNAs can be produced in the host plant. Pairing of these transcripts generates double-stranded RNA, which establishes the sequence relationship required for RNA interference against the corresponding nematode mRNA. Suppression of that target transcript reduces expression of the parasite gene. Agrobacterium has a different role: it is used as the vector that helps introduce the relevant genetic sequences into tobacco. Meloidogyne incognita is the parasitic nematode targeted by the protective strategy. The valid statements follow the engineered gene-delivery and silencing pathway while preserving the distinction between vector and parasite. RNAi protection depends on sequence complementarity between the interfering RNA system and the target mRNA, making the silencing response highly specific. The engineered tobacco example links vector-mediated gene transfer with a natural eukaryotic gene-silencing defence mechanism.
106. The steps below describe establishment of RNAi-based nematode resistance in tobacco:
P. Introduce nematode-specific sequences into tobacco using an Agrobacterium vector
Q. Express complementary sense and antisense RNAs in the transgenic plant
R. Form double-stranded RNA
S. Silence the corresponding nematode mRNA
Which sequence is appropriate?
ⓐ. Q -> P -> S -> R
ⓑ. R -> S -> P -> Q
ⓒ. P -> Q -> R -> S
ⓓ. S -> R -> Q -> P
Correct Answer: P -> Q -> R -> S
Explanation: The strategy starts with transfer of selected nematode-related sequences into tobacco cells using Agrobacterium as a vector. The introduced DNA must then be expressed in the plant to produce complementary sense and antisense transcripts. Pairing of these RNAs generates double-stranded RNA, which supports sequence-specific silencing of the corresponding nematode mRNA. Each stage depends on the preceding one. Silencing cannot occur through the intended engineered mechanism if the relevant sequences were never introduced, and dsRNA cannot form before complementary transcripts are available. The sequence links genetic engineering of the host plant with the RNA-based molecular event that ultimately interferes with parasite gene expression. Sense and antisense transcripts can form double-stranded RNA that triggers suppression of the complementary target message rather than acting as a conventional toxin. Protection of the host follows from suppressing an essential nematode transcript strongly enough to impair parasite survival.
107. Control tobacco plants and RNAi-engineered tobacco plants are deliberately infected with Meloidogyne incognita under the same conditions. After \(5\,\text{days}\), the engineered roots show markedly less evidence of successful nematode establishment. The strongest inference is:
ⓐ. the nematode failed to contact the engineered roots
ⓑ. Agrobacterium itself directly poisoned the nematodes after infection
ⓒ. the transgenic plants produced a universal insecticidal Bt protein
ⓓ. the introduced RNAi system interfered with nematode gene expression and survival
Correct Answer: the introduced RNAi system interfered with nematode gene expression and survival
Explanation: Both groups are deliberately exposed to the same nematode challenge, so reduced establishment in the transgenic roots cannot be explained simply by lack of contact with the parasite. The engineered plants contain the RNAi system designed to generate complementary RNA against a nematode gene. Silencing of the corresponding mRNA can reduce production of an essential parasite gene product and interfere with survival or successful infection. Agrobacterium serves during construction of the transgenic plant rather than acting as a direct nematicide in the experiment. The observation after \(5\,\text{days}\) connects the engineered molecular mechanism with a protective root phenotype under comparable infection pressure. Viral RNA and mobile genetic elements illustrate natural sources of RNA relationships that can participate in sequence-specific silencing.
108. Two tobacco root systems are examined \(5\,\text{days}\) after deliberate infection with Meloidogyne incognita. Root system P is heavily affected, whereas transgenic Root system Q remains comparatively protected. Which molecular sequence best explains the phenotype of Q?
ⓐ. cry-gene expression -> Bt crystal ingestion -> alkaline gut activation in the nematode
ⓑ. complementary dsRNA formation -> nematode mRNA silencing -> reduced parasite survival
ⓒ. protoplast fusion -> somatic-hybrid formation -> destruction of nematode DNA
ⓓ. C-peptide removal -> insulin activation -> inhibition of root infection
Correct Answer: complementary dsRNA formation -> nematode mRNA silencing -> reduced parasite survival
Explanation: The protected transgenic root phenotype is explained by the RNA interference strategy. The host plant produces complementary RNA that forms double-stranded RNA related to an essential nematode gene. Sequence-specific silencing then suppresses the corresponding parasite mRNA, reducing expression of the gene product needed for successful survival in the host. This molecular disruption can account for the reduced infection seen in Root system Q after the same deliberate nematode challenge. The pathway is distinct from Bt toxin activation, somatic hybridisation and insulin processing. The figure-like comparison becomes biologically meaningful when the visible root phenotype is connected with the underlying sequence-specific gene-silencing mechanism. Successful transformation is only the first step; the introduced construct must generate the complementary RNA needed to silence the nematode target.
109. If RNAi in a transgenic tobacco plant successfully suppresses an essential Meloidogyne incognita mRNA, the most direct downstream consequence is:
ⓐ. increased translation of the target nematode gene
ⓑ. conversion of the target mRNA into a cry gene
ⓒ. reduced production of the required gene product and impaired parasite survival
ⓓ. formation of Bt toxin pores in the nematode by the tobacco RNA itself
Correct Answer: reduced production of the required gene product and impaired parasite survival
Explanation: Messenger RNA carries the information required for translation of a gene product. When RNA interference suppresses a specific nematode mRNA, expression of that gene falls and less of the encoded product can be produced. If the targeted gene performs an essential function, this molecular deficiency can prevent the parasite from surviving or establishing successfully in the transgenic host. The consequence follows through a gene-expression pathway rather than through a protein toxin mechanism. RNAi does not convert RNA into cry genes or create Bt-type membrane pores. The protective agricultural effect emerges from selective disruption of parasite gene expression, linking mRNA silencing with reduced nematode survival and improved protection of tobacco roots.
110. Compare the two pest-resistance mechanisms.
| Feature | Bt-based resistance | RNAi-based nematode resistance |
|---|
| P | Uses an insecticidal protein | Uses sequence-specific RNA-mediated silencing |
| Q | Includes activation and action at susceptible insect midgut cells | Includes suppression of a complementary target mRNA |
| R | Depends on a suitable cry gene | Can use nematode-specific sequences introduced into the host |
Which assessment is correct?
ⓐ. P, Q and R all correctly distinguish the two mechanisms
ⓑ. Only P correctly distinguishes the two mechanisms
ⓒ. Only Q and R correctly distinguish the two mechanisms under the stated comparison
ⓓ. None of the rows distinguishes the mechanisms correctly
Correct Answer: P, Q and R all correctly distinguish the two mechanisms
Explanation: Bt-based resistance and RNAi-based resistance can both protect plants from pests, but their molecular mechanisms are fundamentally different. Bt technology relies on an insecticidal protein encoded by an appropriate cry gene. After ingestion by a susceptible insect, the toxin is activated and acts on midgut epithelial cells. RNAi instead uses complementary RNA to suppress a particular target mRNA through sequence-specific gene silencing. In the tobacco-nematode example, nematode-related sequences are introduced into the plant so that protective dsRNA can be produced. All three rows describe genuine mechanistic contrasts. The shared agricultural outcome of pest resistance should not obscure the different molecular routes producing that outcome. Bt protection remains pest specific, so an appropriate Cry protein must be activated and interact successfully with susceptible insect midgut cells. RNA interference depends on sequence complementarity, so protection is specific to transcripts that match the silencing RNA.
111. Crop P controls a susceptible insect by expressing a Bt toxin, while transgenic tobacco Q resists Meloidogyne incognita by producing complementary RNA related to a nematode gene. The most important mechanistic distinction is that:
ⓐ. both systems depend on identical pore-forming proteins
ⓑ. both systems silence parasite mRNA through complementary dsRNA formed inside susceptible insect cells
ⓒ. Bt resistance requires Agrobacterium to remain permanently inside the pest
ⓓ. Bt acts through an insecticidal protein, whereas RNAi acts through sequence-specific gene silencing
Correct Answer: Bt acts through an insecticidal protein, whereas RNAi acts through sequence-specific gene silencing
Explanation: The two systems share the broad goal of protecting a plant from a damaging organism but achieve it through different biological effectors. Bt crops produce an insecticidal protein encoded by a cry gene. In a susceptible insect, that protein is activated and damages the midgut epithelium. The RNAi strategy produces complementary RNA that targets a specific parasite mRNA and suppresses expression of the corresponding gene. The distinction is protein-mediated toxicity versus nucleic-acid-mediated gene silencing. Understanding this difference prevents an important conceptual error: a plant can be pest resistant without using the same molecular mechanism against every pest. The protection must be traced to the particular biological pathway engineered into the host.
112. Two groups of tobacco cells are transformed. Group P receives the complete nematode-specific construct through Agrobacterium and later produces the expected complementary transcripts. In Group Q, transfer of the construct fails completely. After regeneration and nematode challenge, protection is seen only in plants from P. The result most strongly supports the conclusion that:
ⓐ. Agrobacterium must survive permanently in the mature tobacco plant to kill nematodes
ⓑ. nematode infection itself automatically creates the engineered RNAi construct
ⓒ. successful introduction of the nematode-specific sequences is required to establish this transgenic RNAi protection
ⓓ. failure of transformation converts the tobacco plant into a Bt crop
Correct Answer: successful introduction of the nematode-specific sequences is required to establish this transgenic RNAi protection
Explanation: Group P receives the designed nematode-specific sequences and later produces the complementary transcripts required for the intended RNAi pathway. Group Q never receives the construct, so the engineered molecular basis for dsRNA formation and target-mRNA silencing is absent. Protection appearing only in descendants of Group P supports the role of successful gene transfer in establishing the resistant phenotype. The result does not imply that Agrobacterium itself must remain as a nematode-killing organism. Its role is vector-mediated delivery during transformation. The experiment links an early engineering step with a later biological outcome and shows that the protective RNAi system depends on successful introduction and expression of the selected sequences. Successful DNA transfer is only an upstream step; the introduced sequences must also generate the complementary RNA needed for silencing. The engineered tobacco example links vector-mediated gene transfer with a natural eukaryotic gene-silencing defence mechanism.
113. Assess the statements below comparing Bt-mediated resistance with RNAi-mediated resistance.
I. Bt resistance can involve a bacterial toxin protein expressed by a crop.
II. RNAi resistance depends on sequence complementarity to a target mRNA.
III. Bt toxin action and RNAi both protect plants through exactly the same molecular pathway.
IV. RNAi against Meloidogyne incognita can interfere with parasite survival without using the Bt pore-forming mechanism.
Which combination is valid?
ⓐ. I, II and IV only
ⓑ. I and III only
ⓒ. II, III and IV only
ⓓ. I, II and III only
Correct Answer: I, II and IV only
Explanation: Bt and RNAi illustrate two distinct biotechnology strategies for pest resistance. Bt crops can express an insecticidal protein derived from Bacillus thuringiensis. After activation in a susceptible insect, that protein acts on the midgut epithelium and causes membrane damage. RNA interference instead relies on sequence complementarity and suppression of a particular target mRNA. In the Meloidogyne incognita example, silencing an essential nematode gene interferes with parasite survival in transgenic tobacco. The mechanisms converge on plant protection but not on the same molecular pathway. Recognising this distinction is important when interpreting pest-resistant crops, since similar agricultural outcomes can arise from very different forms of engineered biological intervention. The mechanism proceeds from an inactive protoxin to gut activation, epithelial binding and pore-mediated damage, making the order of these events biologically important. RNAi suppresses gene expression through nucleic-acid recognition rather than through the pore-forming protein mechanism used by Bt toxins.
114. A biotechnology company needs a therapeutic molecule in quantities much larger than can be obtained conveniently from its natural source. Which advantage of recombinant DNA technology is most relevant?
ⓐ. It converts every therapeutic molecule into an antibiotic
ⓑ. It enables large-scale production of selected therapeutic products
ⓒ. It eliminates all downstream purification requirements
ⓓ. It restricts therapeutic production to animal tissues
Correct Answer: It enables large-scale production of selected therapeutic products
Explanation: Recombinant DNA technology allows a selected gene associated with a useful therapeutic product to be incorporated into an appropriate biological production system. Once a suitable system is established, the desired molecule can be produced on a scale that would be difficult to achieve by repeatedly collecting small amounts from natural tissues. The important advantage in the scenario is production capacity rather than a change in the biological nature of the therapeutic molecule. Purification may still be required after production, and biotechnology is not restricted to animal tissues. Recombinant production is valuable in healthcare precisely because controlled biological systems can supply important therapeutic molecules in substantial and reproducible quantities. Large-scale production is useful only when the desired product can also be recovered and prepared to the required quality.
115. Four statements are given below about recombinant therapeutics.
I. Recombinant DNA technology can support large-scale production of therapeutic molecules.
II. Recombinant products may provide therapeutics compatible with human use.
III. Recombinant production guarantees that purification is unnecessary.
IV. Recombinant therapeutics can form an important application of medical biotechnology.
Which combination is valid?
ⓐ. I and III only
ⓑ. II and III only
ⓒ. I, III and IV only
ⓓ. I, II and IV only
Correct Answer: I, II and IV only
Explanation: Medical biotechnology uses recombinant DNA technology to produce therapeutically useful molecules efficiently and at large scale. Such products can be designed to correspond closely to human biological molecules, which can improve compatibility compared with some preparations obtained from non-human sources. Recombinant production, however, does not remove the need for downstream recovery and purification. A biological product must still be isolated from the production system and prepared to the required quality. The valid statements describe production scale, therapeutic relevance and potential compatibility, while the incorrect statement confuses recombinant synthesis with final product purification. Production and downstream processing remain distinct parts of a biotechnology process. Recombinant therapeutic production must yield the intended biologically active, human-compatible molecule; successful growth of the engineered host alone is not sufficient. Different biotechnology applications may share genetic engineering while depending on very different downstream biological events.
116. A therapeutic protein isolated from a non-human source causes unwanted immune reactions in some patients. A recombinant form corresponding closely to the human protein is introduced instead. The most direct expected advantage is:
ⓐ. reduced likelihood of reactions caused by recognition of a foreign protein
ⓑ. conversion of the therapeutic protein into a carbohydrate
ⓒ. complete removal of the need for dosage control
ⓓ. automatic correction of the patient's defective gene
Correct Answer: reduced likelihood of reactions caused by recognition of a foreign protein
Explanation: A therapeutic protein derived from another species may differ sufficiently from the human form to be recognised as foreign by a patient's immune system. Producing a human-compatible form through recombinant technology can reduce this source of unwanted immune reaction. The benefit comes from closer molecular compatibility with the patient's own biology, not from changing the protein into another class of molecule or correcting the patient's genome. Recombinant therapy also does not eliminate the need for appropriate dosing. The scenario highlights an important medical advantage of recombinant products: they can provide therapeutics that more closely resemble the human molecules they are intended to replace or supplement.
117. Patient P receives a therapeutic protein purified from a non-human animal source and develops a foreign-protein reaction. Patient Q receives a recombinant human-compatible form with the same therapeutic function and shows no such reaction. The comparison most strongly supports the conclusion that:
ⓐ. all non-human proteins are completely inactive in humans
ⓑ. recombinant therapeutics work only by altering patient DNA
ⓒ. human-compatible recombinant products can reduce some immunological problems associated with non-human preparations
ⓓ. recombinant proteins cannot be recognised by the immune system under any condition
Correct Answer: human-compatible recombinant products can reduce some immunological problems associated with non-human preparations
Explanation: The two preparations serve the same therapeutic purpose, but their biological sources and compatibility differ. A protein obtained from another animal species may contain structural differences that make it more likely to be recognised as foreign. A recombinant product corresponding more closely to the human protein can reduce that particular immunological problem. The evidence does not support the extreme claim that all non-human proteins are inactive or that recombinant proteins can never provoke immune responses. It also does not describe gene therapy, since no patient gene is being corrected. The comparison specifically demonstrates how recombinant production can improve therapeutic compatibility by avoiding some disadvantages of proteins obtained directly from non-human tissues.
118. The following values are given as historical reference data for recombinant therapeutics.
| Context | Approximate number stated |
|---|
| Approved worldwide for human use | \(30\) |
| Marketed in India | \(12\) |
Which interpretation is most appropriate?
ⓐ. The values prove the current global pharmaceutical totals today
ⓑ. The values imply that exactly \(18\) therapeutics were permanently unavailable in India
ⓒ. The values should be treated as historical reference figures rather than a present-day market census
ⓓ. The values show that recombinant therapeutics are no longer used
Correct Answer: The values should be treated as historical reference figures rather than a present-day market census
Explanation: The figures of approximately \(30\) recombinant therapeutics approved worldwide and \(12\) marketed in India are historical data illustrating that recombinant therapeutics had already reached practical medical use. They should not automatically be converted into claims about the complete present-day pharmaceutical market, because approval and marketing status can change over time. Subtracting the two values also cannot reveal why particular products were or were not marketed in India. The biologically important conclusion is that recombinant DNA technology had produced multiple therapeutically useful products for human healthcare. The numbers provide time-specific context for that conclusion rather than a permanent limit. Recombinant therapeutic production must still yield the intended biologically active, human-compatible molecule; successful growth of the engineered production system alone is not enough.
119. A student reads that about \(30\) recombinant therapeutics were approved worldwide and \(12\) were marketed in India in the historical reference. Which use of these numbers is scientifically appropriate?
ⓐ. Use them as contextual evidence that recombinant therapeutics had reached practical medical use
ⓑ. Treat them as permanent values that cannot change over time
ⓒ. Infer that every approved product was identical in function
ⓓ. Conclude that only \(12\) recombinant therapeutics can ever be marketed in India under any circumstances
Correct Answer: Use them as contextual evidence that recombinant therapeutics had reached practical medical use
Explanation: The figures show that recombinant therapeutic products had moved beyond laboratory research into approved human use and commercial availability in the historical period represented by the data. Their value is to demonstrate the practical medical impact of recombinant DNA technology. They should not be treated as timeless limits or as a complete description of current pharmaceutical approval and marketing, as those numbers can change. The figures also provide no basis for assuming that all recombinant therapeutics perform the same function. Scientifically, the sound interpretation is to use the numbers as contextual evidence of adoption while keeping the biological conclusion separate from any claim about present-day market totals or regulatory status.
120. Before recombinant human insulin became available, insulin used for treatment was commonly obtained from:
ⓐ. plant meristems and fungal cultures
ⓑ. transgenic tobacco roots
ⓒ. human lymphocyte cultures
ⓓ. pancreas of cattle and pigs
Correct Answer: pancreas of cattle and pigs
Explanation: Earlier therapeutic insulin preparations were obtained from the pancreas of cattle and pigs. These animal-derived products could perform the required hormonal function, but their non-human origin created a potential disadvantage: structural differences could provoke allergy or other reactions to foreign protein in some patients. Recombinant biotechnology later provided a route for producing human insulin without depending on pancreatic extraction from these animals. The historical animal source is biologically important because it explains one motivation for developing recombinant human insulin. The transition was not merely a change in manufacturing convenience; it also addressed compatibility concerns associated with administering a protein originally isolated from another species.
