Question 1

Plant-made pharmaceuticals: The process in which plant roots are engineered and used as production organs that secrete or accumulate therapeutic proteins is commonly termed what?

Accepted Answer

Introduction / Context: Plant molecular farming uses plants or plant organs to produce high-value proteins such as antibodies, enzymes, and vaccines. Hairy root cultures and whole-root systems can act as living bioreactors, with some platforms designed to secrete the recombinant product into the surrounding medium—an approach termed rhizosecretion. Given Data / Assumptions: Roots can be transformed (e.g., via Agrobacterium rhizogenes) to create fast-growing, hormone-independent cultures. Protein products may be secreted into hydroponic or culture media, simplifying downstream recovery. Concept / Approach: Rhizosecretion exploits the natural secretory pathways of roots, sometimes enhanced by signal peptides and secretion tags, to export recombinant proteins into the medium. This allows continuous harvest without destroying the biomass and can improve product stability and purity relative to whole-leaf extractions. Step-by-Step Solution: Define the production context: roots as production organs for therapeutics.Identify the term that specifically refers to secretion from roots: rhizosecretion.Select “Rhizosecretion.” Verification / Alternative check: Case studies report secretion of antibodies, growth factors, and enzymes from transformed root systems, with media exchange enabling semi-continuous production. Why Other Options Are Wrong: Microcosm establishment: ecological setups, not protein production. Mibridization: not a standard term. Bioremediation: pollutant cleanup using organisms. Phytovolatilization: plants volatilize contaminants, unrelated to protein secretion. Common Pitfalls: Confusing hairy root culture (the biomass platform) with the specific process of secreting recombinant proteins (rhizosecretion). Not all root-based systems are secretion platforms. Final Answer: Rhizosecretion

Question 2

Transgenic crop traits — which of the following is NOT a characteristic introduced via genetic engineering?  Select the option that does not represent a typical, documented trait of genetically modified (GM) crops.

Accepted Answer

Introduction / Context: Transgenic crops (also called genetically modified crops) are engineered to express specific traits that improve agronomic performance, product quality, or nutritional value. Common examples include herbicide tolerance, insect resistance, and enhanced nutritional profiles. Given Data / Assumptions: The listed traits include herbicide resistance, Bt toxin expression, and higher methionine content. Question asks for which option is NOT a characteristic of transgenic crops. We assume mainstream, peer-reviewed or commercially used traits. Concept / Approach: Herbicide-resistant and Bt crops are widely deployed. Nutritional enhancement, including elevated essential amino acids (e.g., methionine, lysine) has been demonstrated in research and some products. Therefore, all provided traits are valid examples of transgenic outcomes. Step-by-Step Solution: List known GM traits: herbicide tolerance, insect resistance, quality and nutrition improvements.Match each option to documented GM traits.Recognize that all examples correspond to real transgenic approaches.Therefore, choose “None of these.” Verification / Alternative check: Commercial portfolios and research literature confirm these categories: HT (herbicide tolerant), Bt (insect resistant), and biofortified crops (amino acids, vitamins) are well established. Why Other Options Are Wrong: Herbicide resistance is a classic GM trait. Bt expression is a hallmark of GM insect control. Increasing methionine has been a goal in oilseeds and cereals via transgenes encoding sulfur-rich storage proteins. Common Pitfalls: Assuming nutrition traits are not “transgenic” because they are less common commercially; many are proven in development pipelines. Final Answer: None of these

Question 3

Herbicide detoxification gene identity — nitrilase is encoded by which bacterial gene source?

Accepted Answer

Introduction / Context: Nitrilases are enzymes that hydrolyze nitriles to corresponding acids and ammonia. In plant biotechnology, bacterial nitrilase genes have been used to detoxify specific herbicides (e.g., bromoxynil) by converting them into less harmful products. Given Data / Assumptions: bxn is historically associated with bromoxynil detoxification. bar/pat genes encode phosphinothricin acetyltransferase and are unrelated to nitrilase. Question seeks the gene that encodes a nitrilase. Concept / Approach: The bxn gene, originally described from Klebsiella (commonly reported as Klebsiella pneumoniae or closely related taxa), encodes a nitrilase that degrades bromoxynil. In contrast, the bar (or pat) genes from Streptomyces encode enzymes that detoxify phosphinothricin (glufosinate) by acetylation, not by nitrile hydrolysis. Step-by-Step Solution: Identify enzyme–gene pairs: nitrilase ↔ bxn; PAT ↔ bar/pat.Confirm that bar/pat do not code for nitrilase.Select the correct pairing: bxn in Klebsiella → nitrilase.Answer: gene bxn in Klebsiella pneumoniae. Verification / Alternative check: Engineering bromoxynil resistance in crops has employed bxn to confer the ability to degrade the herbicide, consistent with nitrilase activity. Why Other Options Are Wrong: bar (and pat) encode phosphinothricin acetyltransferase, not nitrilase; “Both” is incorrect since bar is not a nitrilase gene; “None” is incorrect because bxn is a valid nitrilase gene. Common Pitfalls: Confusing herbicide resistance strategies: nitrilase (nitrile hydrolysis) vs. acetyltransferase (glufosinate detoxification). Final Answer: gene bxn in Klebsiella pneumoniae

Question 4

Constitutive PR protein expression in transgenic plants — what broad effect has been observed?

Accepted Answer

Introduction / Context: Pathogenesis-related (PR) proteins such as chitinases and glucanases are induced during plant defense. Transgenic plants engineered to express PR proteins constitutively can alter baseline immunity and interact with broader defense signaling networks (e.g., systemic acquired resistance). Given Data / Assumptions: Question focuses on the overall outcome of constitutive PR protein expression. Defense is multifactorial; single PR proteins rarely act as universal cures. Defense networks can be primed or cross-activated. Concept / Approach: Constitutive PR expression may enhance resistance by directly degrading pathogen cell walls and by signaling that upregulates additional antimicrobial pathways. The most consistent, generalizable statement is that PR proteins can trigger or prime broader defense responses rather than alone providing universal, high-level protection against diverse pathogens. Step-by-Step Solution: Evaluate each claim against known defense biology.Reject absolutist claims (no protection; universal protection by one PR).Select the nuanced, systems-level effect: defense pathway activation.Answer: PR proteins trigger additional antimicrobial defenses. Verification / Alternative check: Studies report that PR protein expression can prime SAR-like responses and enhance resistance spectrum modestly to moderately, depending on the PR and pathogen. Why Other Options Are Wrong: “No protection” contradicts empirical data; “single PR gives high-level protection to many pathogens” is overstated; the “two PR proteins provide some protection” is too narrow and not a general principle. Common Pitfalls: Overgeneralizing from specific case studies; protection levels vary with PR type, promoter, and pathogen. Final Answer: PR proteins can trigger additional antimicrobial defense pathways in the plant

Question 5

Bruise-resistant tomato development — antisense RNA was targeted against which enzyme to reduce softening?

Accepted Answer

Introduction / Context: Post-harvest softening and bruising in tomatoes are largely due to the breakdown of pectin in the cell wall. The Flavr Savr™ approach used antisense technology to downregulate a key pectin-degrading enzyme and thereby improve firmness. Given Data / Assumptions: Antisense strategy reduces the target mRNA and thus enzyme activity. Polygalacturonase (PG) hydrolyzes pectate chains in the middle lamella. Goal was reduced softening and improved bruise resistance. Concept / Approach: Targeting the polygalacturonase gene by antisense RNA diminishes pectin depolymerization and slows softening. Other listed enzymes do not directly address the main softening pathway in tomato fruit (e.g., SPS affects sucrose metabolism; ACC deaminase modulates ethylene levels, which is indirect). Step-by-Step Solution: Identify the main softening enzyme: polygalacturonase.Recall the antisense downregulation strategy used in early GM tomatoes.Select polygalacturonase as the correct target.Confirm that alternatives do not primarily control pectin depolymerization. Verification / Alternative check: Published reports of Flavr Savr™ document antisense PG reducing softening and extending shelf life. Why Other Options Are Wrong: Glycerol-1-phosphate acyltransferase is for lipid synthesis; ACC deaminase reduces ethylene but is not the core approach used; SPS is unrelated to pectin breakdown; pectin methylesterase is involved in demethylation but the classic antisense target for bruise resistance was PG. Common Pitfalls: Confusing general ethylene manipulation with specific cell-wall enzyme suppression. Final Answer: Polygalacturonase

Question 6

Identifying a breeding approach — selecting a naturally occurring variant with desirable traits and crossing it repeatedly is an example of:

Accepted Answer

Introduction / Context: Crop improvement can occur by conventional breeding or by direct genetic manipulation. Recognizing which process matches a described scenario is fundamental in agricultural biotechnology education. Given Data / Assumptions: A naturally occurring variant is identified in a population. This variant is selectively bred (crossed/selected) to fix the trait. No direct gene transfer or targeted mutagenesis is stated. Concept / Approach: Traditional plant breeding relies on phenotypic selection and hybridization among existing germplasm. Transgenic methods introduce DNA across species or constructs; mutant selection typically follows induced mutagenesis; genome editing applies precise nucleases. None of these are implied in the scenario. Step-by-Step Solution: Match the description to breeding strategies.Note absence of recombinant DNA, mutagens, or gene editing.Identify selective crossing as classical breeding.Choose “Traditional plant breeding.” Verification / Alternative check: Plant breeding textbooks define mass selection and pedigree selection of natural variants as conventional breeding. Why Other Options Are Wrong: Transgenic tech and genome editing involve direct DNA manipulation; mutant selection typically follows induced mutagenesis, which is not stated. Common Pitfalls: Assuming any “improved plant” is transgenic; conventional breeding has produced most of the world’s crop varieties historically. Final Answer: Traditional plant breeding (selection and crossing)

Question 7

Transplastomics in plant biotechnology — which statement best describes this approach and its benefits?

Accepted Answer

Introduction / Context: Transplastomics refers to genetic engineering of the plastid (usually chloroplast) genome rather than the nuclear genome. It is used for high-level protein expression, containment advantages, and multigene operon expression. Given Data / Assumptions: Plastids inherit maternally in many crops, limiting gene flow via pollen. Chloroplasts can accumulate very high levels of recombinant proteins. Approach is distinct from mitochondrial engineering. Concept / Approach: Chloroplast transformation integrates transgenes into the plastome, enabling high expression (due to polyploidy of plastids) and, in many species, reduced transgene pollen transmission. It has practical applications in vaccine production, metabolic engineering, and trait stacking. Step-by-Step Solution: Identify the organelle genome targeted: plastid (chloroplast).Recall benefits: high expression, operon engineering, maternal inheritance.Select the statement that captures these features.Reject options claiming low yields, ubiquitous pollen spread, or negligible utility. Verification / Alternative check: Peer-reviewed demonstrations show multi-percent total soluble protein accumulation of recombinant products in plastids, validating high yield claims. Why Other Options Are Wrong: Low yield is incorrect; most chloroplast transgenics are not pollinated via plastid DNA due to maternal inheritance; practical uses are abundant; mitochondria are not the main target in “transplastomics.” Common Pitfalls: Confusing plastid transformation with nuclear transformation or mitochondrial engineering. Final Answer: Targets genes in the chloroplast (plastid) genome for high-level, often maternal, expression

Question 8

Cell-based energy competence — which technology creates cytoplasmic hybrids with enhanced organelle-based energy capacity?

Accepted Answer

Introduction / Context: Some breeding and biotechnology methods aim to combine nuclear and cytoplasmic components from different parents. Cytoplasmic hybrids (cybrids) can acquire mitochondria or plastids that improve energy metabolism or cytoplasmic male sterility traits. Given Data / Assumptions: Energy harnessing is largely tied to mitochondria (respiration) and plastids (photosynthesis). Cybridization specifically produces hybrids with mixed or selected cytoplasmic organelles. Terminology must distinguish general protoplast fusion from the selection of cytoplasmic hybrids. Concept / Approach: Cybridization involves protoplast fusion followed by selection for desired cytoplasm (mitochondria/chloroplasts), potentially enhancing respiratory or photosynthetic efficiency or introducing CMS. While protoplast fusion is the physical technique, “cybridization” denotes the outcome emphasizing cytoplasmic exchange. Step-by-Step Solution: Identify the goal: enhance organelle-based energy capacity.Map to method: generate cytoplasmic hybrids (cybrids).Select cybridization as the most precise term.Recognize that generic protoplast fusion does not specify cytoplasmic selection. Verification / Alternative check: Classical plant cell culture literature describes cybrids with novel mitochondrial/plastid complements improving metabolic traits. Why Other Options Are Wrong: “Chlybridization” is uncommon/ambiguous terminology; “protoplast fusion” is generic; “Mibridization” is not standard; somatic embryogenesis does not create cytoplasmic hybrids. Common Pitfalls: Using the umbrella term (protoplast fusion) when the intended outcome is specifically a cytoplasmic hybrid. Final Answer: Cybridization (fusion yielding cytoplasmic hybrids)

Question 9

Engineering herbicide resistance in transgenic plants — which strategic approaches are used?

Accepted Answer

Introduction / Context: Herbicide resistance traits can be engineered using multiple strategies, each addressing a different point in the herbicide–plant interaction: target modification, target overproduction, or metabolism-based detoxification. Given Data / Assumptions: Target enzymes include EPSPS (glyphosate) or ALS (sulfonylureas/imazapyrs). Detox enzymes include PAT/Bar (glufosinate) or other degradative enzymes. Overexpression sometimes buffers partial inhibition. Concept / Approach: All listed strategies have precedents: insensitive EPSPS mutations, ALS variants, or overexpression; and detoxification by acetyltransferases or oxygenases. Therefore, the comprehensive answer is that all can be used depending on herbicide mode of action. Step-by-Step Solution: List known resistance mechanisms.Match each to real-world examples.Conclude that multiple avenues are valid.Select “All of the above.” Verification / Alternative check: Commercial crops exhibit target-site mutations (EPSPS, ALS) and detoxification (bar/pat) strategies. Why Other Options Are Wrong: Each individual option is correct, so “None” and single-option choices are incomplete. Common Pitfalls: Assuming one universal method; herbicides act via distinct targets requiring tailored strategies. Final Answer: All of the above

Question 10

Environmental simulation in the lab — the term for a small setup that mimics a particular ecosystem is:

Accepted Answer

Introduction / Context: Ecologists and environmental biotechnologists often use controlled, scaled-down systems to model ecosystem processes such as nutrient cycling, pollutant fate, or species interactions under reproducible conditions. Given Data / Assumptions: A “small laboratory setup” that simulates an environment is sought. Terms listed include process names and unrelated jargon. We need the standard ecological term. Concept / Approach: A microcosm is a miniature, simplified ecosystem used experimentally to study ecological dynamics. It contrasts with “bioremediation” (a process to clean pollutants), “rhizosecretion” (root-mediated exudation), and nonstandard/irrelevant terms like “mibridization.” Step-by-Step Solution: Identify the definition: mini-ecosystem model.Map to standard term: microcosm.Exclude process terms unrelated to simulation setup.Answer: Microcosm. Verification / Alternative check: Textbooks and reviews use “microcosm” and “mesocosm” to describe controlled ecological test systems at different scales. Why Other Options Are Wrong: Bioremediation is an application, not a model; rhizosecretion is a plant physiology term; “mibridization” is not a standard concept; chemostat is a continuous culture device for microbes, not necessarily an ecosystem simulation. Common Pitfalls: Confusing microcosms with general microbial culture devices. Final Answer: Microcosm

Question 11

Engineering resistance to L-phosphinothricin (glufosinate) in tobacco — which gene transfer has been used to confer resistance?

Accepted Answer

Introduction / Context: Phosphinothricin (PPT, glufosinate) is a nonselective herbicide that inhibits glutamine synthetase (GS), leading to ammonia accumulation and plant death. Several strategies exist to engineer crop tolerance to this herbicide. Given Data / Assumptions: Commercially, bar/pat genes (phosphinothricin acetyltransferase) are widely used, but they are not among the options. The biochemical target of PPT is GS. Altering or compensating for the target enzyme can impart tolerance. Concept / Approach: Because PPT inhibits GS, engineering plants with GS variants or overexpression can mitigate toxicity by maintaining glutamine synthesis. While EPSPS relates to glyphosate and ALS to sulfonylurea/imidazolinone herbicides, GS is the direct target of PPT and has been explored to enhance tolerance in research settings when bar/pat are not used. Step-by-Step Solution: Identify herbicide mode of action: PPT inhibits GS.Exclude unrelated targets: EPSPS (glyphosate), ALS (SU/IMI herbicides).Select the gene aligned with PPT’s target: GS.Answer: Gene for GS (glutamine synthetase). Verification / Alternative check: Although bar/pat are the dominant commercial solution, literature shows that modifying GS expression or insensitivity can contribute to tolerance in experimental systems. Why Other Options Are Wrong: EPSPS and ALS confer tolerance to different herbicide classes; “Any of the above” is incorrect because only GS directly aligns with PPT’s target among the listed genes. Common Pitfalls: Assuming all herbicide resistance relies on the same target modifications; each herbicide class has specific targets. Final Answer: Gene for GS (glutamine synthetase)

Question 12

In plant biotechnology, which gene product specifically detoxifies the herbicide bromoxynil in transgenic plants?

Accepted Answer

Introduction / Context: Bromoxynil is a nitrile herbicide. When breeders engineer herbicide-tolerant crops, the key is to express an enzyme that inactivates the specific toxicant. Knowing which gene works on which herbicide is essential for correct trait design and for avoiding regulatory or stewardship errors. Given Data / Assumptions: Bromoxynil contains a nitrile functional group. Engineered tolerance relies on enzymes that transform or sequester the active herbicide. Common detoxification genes include nitrilase (bxn), GSTs, and phosphinothricin acetyl transferase (bar/pat), each with distinct substrate specificity. Concept / Approach: Enzyme–substrate specificity determines herbicide tolerance. Nitrilases hydrolyze nitriles to corresponding acids and ammonia, directly targeting the nitrile group in bromoxynil. In contrast, GSTs catalyze glutathione conjugation, commonly used for chloroacetanilides and other classes, and phosphinothricin acetyl transferase detoxifies glufosinate (phosphinothricin) by acetylation, not bromoxynil. Step-by-Step Solution: Identify the herbicide's functional group: bromoxynil is a nitrile.Match enzyme chemistry: nitrilase hydrolyzes nitriles to acids.Exclude unrelated detox pathways: GST conjugation and PAT acetylation do not primarily target bromoxynil.Therefore select the gene encoding nitrilase as the correct molecular tool. Verification / Alternative check: Classic bxn genes from soil bacteria confer bromoxynil tolerance; field and greenhouse data show survival of transformed plants after bromoxynil applications when nitrilase is expressed. Why Other Options Are Wrong: B: GSTs aid detox for other herbicide classes; bromoxynil is not the primary target. C: Phosphinothricin acetyl transferase is specific to glufosinate, a different chemistry. D/E: Over-inclusive or incorrect; specificity matters in herbicide tolerance. Common Pitfalls: Assuming any generic “detox” enzyme works for all herbicides; overlooking functional group specificity leads to failed field tolerance. Final Answer: Nitrilase

Transgenic Plant Questions