​CSIR NET Life Sciences Unit 3 Fundamental Processes Mock Test 2026: Free Interactive Practice Paper, PYQ Solutions & Practice Online

CSIR NET Life Sciences Mock Test: Unit 3 Fundamental Processes

Practice High-Yield Interactive Questions for CSIR UGC NET, GATE XL & DBT BET

Unit 3: Fundamental Processes 50 Standard Questions Interactive Test Instant Explanations

Exam Instructions & Marking Scheme:

• Part A (Q1-Q10): General Science & Aptitude | +2 Marks | -0.5 Negative Marking
• Part B (Q11-Q35): Subject Core Concepts | +2 Marks | -0.5 Negative Marking
• Part C (Q36-Q50): Advanced Analytical & Problem Solving | +5 Marks | -1.0 Negative Marking
• How to use: Click on your chosen option to reveal the correct answer and detailed explanation instantly.

PART A: General Science & Aptitude Q1 - Q10 (2 Marks Each)

Q1. A DNA sequencing reaction runs for 120 minutes. If the rate of polymerization is increased by 25%, how much time will be required to complete the exact same reaction?

Q2. In a molecular biology laboratory, 4 researchers can extract RNA from 16 tissue samples in 4 hours. How many tissue samples can 6 researchers process in 6 hours assuming identical working efficiency?

Q3. A researcher prepares a stock buffer solution containing 20% ethanol by volume. If 200 mL of pure water is added to 800 mL of this buffer solution, what is the final concentration of ethanol in the diluted solution?

Q4. Find the missing number in the following biochemical experimental sequence: 3, 7, 15, 31, 63, ?

Q5. A culture containing bacterial cells doubles every 20 minutes. If a culture tub is completely full of bacterial culture at 4:00 PM, at what time was the culture tub exactly half full?

Q6. In a plasmid map, Restriction Site X is located at position 1200 bp and Restriction Site Y is at position 3800 bp in a circular plasmid of total size 6000 bp. What are the expected fragment sizes upon complete digestion with both enzymes?

Q7. Statements: All enzymes are proteins. Some proteins are hormones. Conclusions: I. Some enzymes are hormones. II. All proteins are enzymes.

Q8. If the word "REPLICATION" is coded as "SFQMJDBUJPO" in a cryptic molecular code, how is the word "TRANSCRIPTION" coded using the exact same rule?

Q9. The average absorbance reading of 5 protein standard samples is 0.40. When a 6th sample is included, the average absorbance increases to 0.45. What is the absorbance of the 6th sample?

Q10. A laboratory centrifuge rotates at a speed of 12000 rpm. What angle in radians does the rotor turn through in 1 second?

PART B: Subject Core Concepts Q11 - Q35 (2 Marks Each)

Q11. Which DNA polymerase enzyme in Escherichia coli possesses 5' to 3' exonuclease activity required for primer removal during lagging strand synthesis?

Q12. During eukaryotic DNA replication, which protein complex functions as the replicative helicase unwinding double-stranded DNA at the replication fork?

Q13. What is the specific role of the beta subunit sliding clamp in the E. coli DNA Polymerase III holoenzyme complex?

Q14. In bacterial transcription initiation, which specific domain of the sigma factor subunit recognizes and binds directly to the -10 promoter region (Pribnow box)?

Q15. Which eukaryotic RNA polymerase is responsible for the transcription of transfer RNA (tRNA) and 5S ribosomal RNA (5S rRNA) genes?

Q16. Alpha-amanitin, a toxic peptide isolated from Amanita phalloides mushrooms, acts as a potent inhibitor of eukaryotic transcription by targeting which enzyme primarily?

Q17. What specialized structural modification is added to the 5' end of eukaryotic pre-mRNA immediately after initiation of transcription?

Q18. During pre-mRNA splicing in eukaryotes, the nucleophilic attack on the 5' splice site donor sequence is executed by the 2'-OH group of which specific residue?

Q19. Aminoacyl-tRNA synthetases ensure translational fidelity through a two-step proofreading mechanism. Where is the high-energy ester bond formed in aminoacyl-tRNA?

Q20. In prokaryotic translation initiation, which ribosomal RNA sequence base-pairs directly with the Shine-Dalgarno sequence located upstream of the AUG start codon on mRNA?

Q21. Which elongation factor in bacterial protein synthesis delivers aminoacyl-tRNA to the A-site of the ribosome in a GTP-dependent manner?

Q22. Antibiotic Puromycin causes premature chain termination during protein synthesis by mimicking the chemical structure of which molecular component?

Q23. In the E. coli lac operon, what molecule acts as the true intracellular allosteric inducer that binds to and inactivates the Lac repressor protein?

Q24. In the bacterial trp operon, transcriptional attenuation depends on the formation of specific secondary hairpin structures in the leader RNA. Which stem-loop hairpin acts as the transcription termination signal?

Q25. Which histone post-translational modification is predominantly associated with transcriptional activation and chromatin relaxation (euchromatin formation)?

Q26. Base Excision Repair (BER) pathway initiates lesion repair via the action of which specific enzyme that cleaves the N-glycosidic bond?

Q27. Nucleotide Excision Repair (NER) in E. coli utilizes the UvrABC excinuclease complex. Which protein component acts as the lesion sensor that scans DNA?

Q28. In E. coli Mismatch Repair (MMR), how does the MutH endonuclease distinguish the newly synthesized daughter strand from the parental template strand?

Q29. What is the catalytic core protein responsible for strand exchange in homologous recombination in Escherichia coli?

Q30. Which protein complex processes double-stranded DNA breaks into 3' single-stranded DNA overhangs required for RecA filament loading in E. coli?

Q31. Autonomous DNA transposons in prokaryotes and eukaryotes encode which essential enzyme required for their own excision and integration?

Q32. Retrotransposons move within a genome via an RNA intermediate using which key enzymatic activity?

Q33. What feature is characteristic of long terminal repeat (LTR) retrotransposons like Ty elements in yeast?

Q34. In eukaryotic RNA interference (RNAi), which RNase III endonuclease processes long double-stranded precursor RNA (pre-miRNA) in the cytoplasm into functional duplex siRNA/miRNA?

Q35. What is the catalytic protein component of the RNA-induced silencing complex (RISC) responsible for mRNA cleavage guided by small RNAs?

PART C: Advanced Analytical & Problem Solving Q36 - Q50 (5 Marks Each)

Q36. In a Meselson-Stahl density gradient centrifugation experiment, E. coli cells grown for many generations in 15N heavy isotope medium are transferred to 14N light isotope medium. What distribution of DNA molecules (Heavy-Heavy, Heavy-Light, Light-Light) will be observed after exactly 3 generations of replication in 14N medium?

Q37. A temperature-sensitive mutant of E. coli fails to synthesize Okazaki fragments at the restrictive temperature of 42 degrees C. Analysis reveals that unwinding at the fork is normal, leading strand synthesis continues normally, but RNA primers are synthesized and remain unextended on the lagging strand template. Which enzyme is defective in this mutant strain?

Q38. Consider a cell-free transcription assay using eukaryotic RNA Polymerase II. Mutation A is introduced into the TATA box (-30 region), Mutation B into the Inr element (+1 region), and Mutation C into the C-terminal domain (CTD) heptapeptide repeats of RNA Pol II (all Serine-5 residues converted to Alanine). Which combination of functional outcomes is CORRECT?

Q39. An in vitro translation system programmed with a synthetic polyribonucleotide sequence 5'-AUG(UC)10-3' yields a polypeptide chain. What specific sequence of amino acids will be produced from this reading frame starting at the AUG codon?

Q40. You are analyzing E. coli merozygotes (partial diploids) for lac operon regulation. Strain genotype: I+ P+ O^c Z+ Y- / I- P+ O+ Z- Y+. (Where I+ = wild type repressor, I- = null repressor, O^c = constitutive operator, Z = beta-galactosidase, Y = permease). How will beta-galactosidase (Z) and permease (Y) be expressed in the absence and presence of IPTG inducer?

Q41. In E. coli trp operon attenuation, what occurs at the molecular level when intracellular Tryptophan concentrations are extremely LOW?

Q42. Human fibroblasts exposed to UV radiation suffer thymine dimer formation. In an experiment, cells from Xeroderma Pigmentosum (XP) Group A and XP Group C mutants are fused to form heterokaryons. The fused heterokaryon cells show normal levels of unscheduled DNA synthesis (UDS) after UV exposure. What genetic phenomenon explains this result?

Q43. A researcher isolates an E. coli mutant with a defective MutS protein. When this mutant strain undergoes multiple rounds of cell division, which specific cellular defect will be predominantly observed?

Q44. During RecBCD-mediated homologous recombination in E. coli, what crucial event occurs when the RecBCD complex encounters a Chi site (5'-GCTGGGGG-3') on the unwinding DNA strand?

Q45. An investigator constructs a synthetic gene lacking introns and inserts it downstream of a strong promoter in a mammalian plasmid expression vector. Upon transfection, high mRNA levels are detected in the nucleus, but protein expression is extremely low in the cytoplasm. Addition of an intron-containing cassette restores robust protein expression. What post-transcriptional process accounts for this dependency?

Q46. In a eukaryotic cell line, a specific microRNA (miRNA) exhibits 100% perfect sequence complementarity to the 3' UTR of Target Gene X mRNA. In a second cell line, a different miRNA exhibits partial non-consecutive mismatch complementarity to Target Gene Y mRNA. What are the predicted outcomes on Target X and Target Y regulation?

Q47. Bacterial IS elements (Insertion Sequences) contain Inverted Terminal Repeats (ITRs) at their ends and generate Direct Repeats (DRs) in host genomic DNA upon insertion. What is the molecular origin of the host Direct Repeats (DRs)?

Q48. In eukaryotic translation, the internal ribosome entry site (IRES) element allows translation initiation under cellular stress conditions (such as viral infection or apoptosis) when canonical initiation is inhibited. Which standard translation initiation factor complex is bypassed when IRES-mediated translation occurs?

Q49. You test three eukaryotic transcription inhibitors in nuclear extract assays: Inhibitor X blocks TFIIH kinase activity. Inhibitor Y prevents TBP binding to TATA box. Inhibitor Z blocks P-TEFb kinase activity. Which step of transcription will be blocked by each inhibitor (X, Y, Z) respectively?

Q50. Chromatin Immunoprecipitation (ChIP) assay followed by qPCR was performed using antibodies against total Histone H3, Acetylated Histone H3 (H3K9ac), and Trimethylated Histone H3 (H3K9me3) on Promoter P1 (active gene) and Promoter P2 (silenced gene). What binding profiles do you predict?

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