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Engineering Ultimate Exam
Question 1. Which of the following best describes the structural difference between B-DNA and Z-DNA? A) B-DNA is right-handed, Z-DNA is left-handed B) B-DNA contains thymine, Z-DNA contains uracil C) B-DNA has a wide major groove, Z-DNA has a narrow minor groove D) B-DNA is single-stranded, Z-DNA is double-stranded Answer: A Explanation: B-DNA adopts a right-handed helix, whereas Z-DNA adopts a left-handed conformation; the other statements are incorrect. Question 2. What property makes RNA chemically less stable than DNA? A) Presence of a 2′-hydroxyl group on ribose B) Absence of phosphodiester bonds C) Double-stranded nature of RNA D) Use of thymine instead of uracil Answer: A Explanation: The 2′-hydroxyl group in RNA makes the backbone susceptible to hydrolysis, decreasing its stability compared to DNA. Question 3. Which enzyme relieves positive supercoiling ahead of a replication fork in bacteria? A) DNA ligase B) DNA polymerase I C) DNA gyrase (a type II topoisomerase) D) RNase H Answer: C
Engineering Ultimate Exam
Explanation: DNA gyrase introduces negative supercoils, removing positive supercoils that accumulate ahead of the fork. Question 4. In eukaryotes, which DNA element primarily defines the boundaries of a chromatin domain called a topologically associating domain (TAD)? A) Origin of replication B) CTCF binding sites C) Poly-A signal D) Ribosomal RNA gene cluster Answer: B Explanation: CTCF (CCCTC-binding factor) together with cohesin demarcates TAD boundaries, influencing 3D genome organization. Question 5. Which of the following is a characteristic of SINEs (Short Interspersed Nuclear Elements)? A) Encode reverse transcriptase B) Are typically >10 kb in length C) Originate from tRNA or 7SL RNA sequences D) Are only found in prokaryotic genomes Answer: C Explanation: SINEs are non-autonomous retrotransposons derived from small RNAs such as tRNA; they lack coding capacity for reverse transcriptase. Question 6. Which histone modification is most commonly associated with transcriptional activation? A) H3K9 methylation B) H3K27 trimethylation
Engineering Ultimate Exam
A) 10–15 bp B) 25–35 bp C) 50–60 bp D) 100–120 bp Answer: B Explanation: The TATA box is typically positioned 25–35 bp upstream of the transcription start site, serving as a binding site for TBP. Question 10. Which of the following processes generates a mature 5′-capped mRNA? A) Splicing of introns B) Poly-A tail addition C) Addition of 7-methylguanosine by capping enzymes in the nucleus D) Removal of the 5′-phosphate by exonuclease Answer: C Explanation: The 5′-cap (7-methylguanosine) is added co-transcriptionally to protect mRNA and facilitate translation. Question 11. The wobble hypothesis explains degeneracy of the genetic code at which position of the codon? A) First base B) Second base C) Third base D) All three bases equally Answer: C Explanation: The third base of a codon often tolerates non-standard base pairing, allowing one tRNA to recognize multiple codons.
Engineering Ultimate Exam
Question 12. Which type of restriction endonuclease recognizes a specific DNA sequence and cuts at a defined distance away from that site? A) Type I B) Type II C) Type III D) Type IV Answer: C Explanation: Type III enzymes recognize a specific sequence and cleave a short distance downstream (typically 20–30 bp). Question 13. The plasmid pUC19 contains the lacZ α-fragment for blue/white screening. What does a white colony indicate? A) The plasmid carries an insert disrupting lacZ α B) The plasmid failed to transform the host C) The host strain lacks β-galactosidase activity D) The insert is present but does not affect lacZ α Answer: A Explanation: Insertion of a DNA fragment into the multiple cloning site disrupts the lacZ α gene, preventing α-complementation and resulting in white colonies on X-gal/IPTG plates. Question 14. Which viral vector is most commonly used for stable integration into the host genome in mammalian gene therapy? A) Adenovirus B) Adeno-associated virus (AAV) C) Lentivirus (derived from HIV) D) Vaccinia virus Answer: C
Engineering Ultimate Exam
C) Integration of donor DNA D) Transcription of the target gene Answer: B Explanation: Cas9 recognizes and binds DNA only when a PAM (e.g., NGG for SpCas9) is present immediately downstream of the target sequence, enabling cleavage. Question 18. Which DNA repair pathway is predominantly used after a double-strand break created by CRISPR-Cas9 when no donor template is supplied? A) Homology-Directed Repair (HDR) B) Base Excision Repair (BER) C) Non-Homologous End Joining (NHEJ) D) Mismatch Repair (MMR) Answer: C Explanation: In the absence of a repair template, cells primarily employ NHEJ, which ligates the broken ends and often introduces insertions/deletions. Question 19. Zinc-finger nucleases (ZFNs) achieve DNA specificity through: A) RNA-guided base pairing B) Protein-DNA interactions mediated by zinc-finger domains C) Recognition of methylated CpG islands D) Binding to palindromic DNA sequences only Answer: B Explanation: Each zinc-finger domain recognizes a 3-bp DNA motif; arrays of these domains confer sequence specificity.
Engineering Ultimate Exam
Question 20. Which of the following RNA molecules is directly involved in the RNA-induced silencing complex (RISC) to mediate target mRNA cleavage? A) siRNA (small interfering RNA) B) tRNA C) snRNA D) rRNA Answer: A Explanation: siRNAs are incorporated into RISC, guiding the complex to complementary mRNA for endonucleolytic cleavage. Question 21. Morpholino antisense oligonucleotides differ from traditional DNA antisense molecules because they: A) Contain a phosphorothioate backbone B) Form RNA-DNA hybrids C) Have a morpholine ring and non-ionic backbone, making them resistant to nucleases D) Are incorporated into the genome by reverse transcription Answer: C Explanation: Morpholinos possess a morpholine ring and charge-neutral phosphorodiamidate linkages, providing high stability and preventing RNase degradation. Question 22. In Agrobacterium-mediated plant transformation, the T-DNA region that integrates into the plant genome is located between which two border sequences? A) Left and right border (LB and RB) B) Origin of replication and selectable marker C) Promoter and terminator
Engineering Ultimate Exam
A) Michaelis-Menten B) Hill equation C) Lineweaver-Burk D) Briggs-Haldane Answer: A Explanation: The Monod model μ = μmax S/(Ks + S) mirrors Michaelis-Menten kinetics for enzyme-substrate reactions. Question 26. In downstream processing, which chromatography technique separates proteins based on their net charge at a given pH? A) Size-exclusion chromatography B) Affinity chromatography C) Ion-exchange chromatography D) Hydrophobic interaction chromatography Answer: C Explanation: Ion-exchange chromatography exploits electrostatic interactions between protein surface charges and oppositely charged resin groups. Question 27. Which of the following is a primary advantage of using a His-tag for recombinant protein purification? A) High affinity for cellulose B) Specific binding to nickel-nitrilotriacetic acid (Ni-NTA) resin under mild conditions C) Ability to catalyze protein folding D) Enables direct visualization on SDS-PAGE without staining Answer: B Explanation: A poly-histidine tag (6×His) binds Ni²⁺-NTA with high specificity, allowing purification under non-denaturing conditions.
Engineering Ultimate Exam
Question 28. The production of the antibiotic erythromycin in Saccharopolyspora erythraea is enhanced by overexpressing which type of enzyme? A) DNA polymerase B) Polyketide synthase C) Ribosomal RNA methyltransferase D) Glucose- 6 - phosphate dehydrogenase Answer: B Explanation: Erythromycin is a polyketide; increasing the activity of the polyketide synthase pathway boosts its biosynthesis. Question 29. Which microorganism is commonly engineered for butanol production via the ABE (acetone-butanol-ethanol) fermentation process? A) Escherichia coli B) Clostridium acetobutylicum C) Saccharomyces cerevisiae D) Corynebacterium glutamicum Answer: B Explanation: Clostridium acetobutylicum naturally performs the ABE fermentation and is a primary chassis for industrial butanol production. Question 30. Golden Rice was engineered to produce β-carotene in the endosperm by introducing genes from which two organisms? A) Zea mays and Arabidopsis thaliana B) Daï (daffodil) and Erwinia uredovora (now Pantoea ananatis) C) Bacillus subtilis and Nicotiana tabacum D) Ricinus communis and Chlamydomonas reinhardtii
Engineering Ultimate Exam
A) Bacteriophages are engineered to carry antibody-encoding DNA fused to a coat protein, allowing displayed antibody fragments on the phage surface for binding selection. B) Phages infect mammalian cells, integrating antibody genes into the host genome. C) Phages are used to lyse bacterial cultures, releasing intracellular antibodies. D) Phages randomly mutate antibody genes, and the most stable variants are selected. Answer: A Explanation: Phage display fuses antibody fragments to a phage coat protein, presenting them on the virion surface for affinity selection against antigens. Question 34. In the production of recombinant human insulin using E. coli, why is a signal peptide not required for secretion? A) Insulin is secreted via the Sec pathway automatically. B) E. coli lacks a secretory pathway for eukaryotic proteins, so insulin is produced as inclusion bodies and later refolded. C) The insulin gene includes its own bacterial signal peptide. D) Insulin is synthesized in the periplasm by default. Answer: B Explanation: E. coli does not efficiently secrete eukaryotic proteins; insulin is expressed as insoluble inclusion bodies, which are harvested and refolded in vitro. Question 35. Which viral vector is most commonly used for delivering mRNA vaccines into host cells? A) Adenovirus B) Lentivirus
Engineering Ultimate Exam
C) Lipid nanoparticle (non-viral) delivery system D) Baculovirus Answer: C Explanation: mRNA vaccines are typically encapsulated in lipid nanoparticles, not viral vectors, to protect RNA and facilitate cellular uptake. Question 36. The term “CAR” in CAR-T cell therapy stands for: A) Cytokine-Activated Receptor B) Chimeric Antigen Receptor C) Cellular Antigen Regulator D) Constitutive Activation Region Answer: B Explanation: CAR-T cells are engineered to express a chimeric antigen receptor that combines an antibody-derived binding domain with T-cell signaling motifs. Question 37. Which biosafety level (BSL) requires work in a Class III biosafety cabinet and full-body, air-supplied suits? A) BSL- 1 B) BSL- 2 C) BSL- 3 D) BSL- 4 Answer: D Explanation: BSL-4 is for the most dangerous pathogens; it mandates Class III cabinets, positive-pressure suits, and dedicated facilities. Question 38. In the context of GMO environmental risk, which of the following is a primary concern regarding gene flow?
Engineering Ultimate Exam
Question 41. In a BLAST (Basic Local Alignment Search Tool) search, the “E-value” represents: A) The number of exact matches found B) The probability that the alignment occurred by chance; lower values indicate more significant similarity C) The length of the query sequence D) The percentage of GC content in the alignment Answer: B Explanation: The E-value estimates how many alignments with a given score would be expected by random chance; smaller E-values denote higher significance. Question 42. AlphaFold has revolutionized protein structure prediction by primarily using which type of artificial intelligence? A) Convolutional neural networks (CNNs) B) Recurrent neural networks (RNNs) C) Deep residual networks combined with attention mechanisms D) Support vector machines (SVMs) Answer: C Explanation: AlphaFold employs deep residual networks and attention-based architectures to infer inter-residue distances and angles, achieving near-experimental accuracy. Question 43. In metabolomics, the term “flux” refers to: A) The total number of metabolites detected in a sample B) The rate at which metabolites are converted through a pathway C) The pH of the extraction buffer D) The molecular weight distribution of metabolites
Engineering Ultimate Exam
Answer: B Explanation: Metabolic flux quantifies the speed of substrate-to-product conversion, often measured using isotopic labeling. Question 44. Which of the following best describes a “dominant-negative” mutation in a protein? A) The mutant protein gains a new function. B) The mutant protein interferes with the function of the wild-type protein, often by forming non-functional complexes. C) The mutation only manifests in homozygous individuals. D) The mutation leads to increased degradation of mRNA. Answer: B Explanation: Dominant-negative alleles produce a defective protein that dimerizes or otherwise interacts with the normal protein, inhibiting its activity. Question 45. In the context of plant molecular markers, AFLP (Amplified Fragment Length Polymorphism) combines which two techniques? A) RFLP and PCR B) RAPD and Southern blotting C) Restriction digestion followed by selective PCR amplification of fragments D) Microsatellite analysis and sequencing Answer: C Explanation: AFLP digests genomic DNA with restriction enzymes, ligates adapters, and then selectively amplifies subsets of fragments via PCR. Question 46. Which of the following statements about somatic cell nuclear transfer (SCNT) is correct?
Engineering Ultimate Exam
Explanation: The FDA reviews BLAs for safety, efficacy, and manufacturing quality of biologic products before market approval. Question 49. Which of the following is a key advantage of using a yeast artificial chromosome (YAC) over a bacterial artificial chromosome (BAC) for cloning large DNA fragments? A) Higher copy number in the host cell B) Ability to propagate fragments >1 Mb, encompassing entire eukaryotic gene loci with regulatory elements C) Compatibility with E. coli replication origin D) Resistance to restriction enzyme digestion Answer: B Explanation: YACs can maintain very large inserts (up to several megabases), preserving native chromatin context and regulatory sequences, whereas BACs typically hold up to ~300 kb. Question 50. The “P-value” in a statistical test of differential gene expression indicates: A) The probability that the observed difference is due to random chance; lower values suggest significance. B) The proportion of genes that are up-regulated. C) The fold-change magnitude. D) The sequencing depth of the RNA-seq experiment. Answer: A Explanation: A low P-value (<0.05 commonly) means the null hypothesis (no difference) can be rejected, implying true differential expression. Question 51. Which of the following best describes the function of a “riboswitch” in bacterial gene regulation?
Engineering Ultimate Exam
A) A protein that binds DNA to repress transcription. B) An RNA element that changes conformation upon ligand binding, influencing transcription termination or translation initiation. C) A small peptide that degrades mRNA. D) A membrane transporter for amino acids. Answer: B Explanation: Riboswitches are regulatory RNA sequences that bind metabolites and alter their structure to modulate gene expression. Question 52. In a typical qPCR (quantitative real-time PCR) assay using SYBR Green, fluorescence increases because: A) SYBR Green intercalates into double-stranded DNA, and the amount of product correlates with fluorescence intensity. B) SYBR Green binds to single-stranded RNA. C) The dye is released from a quencher upon amplification. D) SYBR Green is incorporated into the DNA polymerase active site. Answer: A Explanation: SYBR Green fluoresces only when bound to double-stranded DNA, allowing real-time monitoring of product accumulation. Question 53. Which of the following is a characteristic of a “self-splicing” intron? A) Requires the spliceosome for removal. B) Catalyzes its own excision without protein factors (ribozymes). C) Is always located in the 5′-UTR. D) Produces a circular RNA product. Answer: B
