CSIR NET Life Science Most Repeated Questions with Topic Analysis

The CSIR NET June 2026 Life Sciences examination will be conducted by the National Testing Agency (NTA) on July 17, 2026, in the morning shift from 09:00 AM to 12:00 Noon.

For many candidates, the challenge is not covering the syllabus but identifying the topics that appear repeatedly in the examination. Previous years' questions provide valuable insight into recurring concepts, experimental question formats, and subjects that receive consistent weightage.

This six-paper analysis of approximately 870 questions from June 2023 to December 2025 highlights the most repeated topics, important concepts, high-weightage subjects, and frequently tested question patterns to help candidates focus their revision before the examination.

CSIR NET Life Science Exam Pattern and Question Distribution 

The CSIR NET Life Sciences paper consists of three sections.

Recent papers indicate that Part C contributes a significant portion of the overall difficulty. Candidates should therefore spend adequate time practicing analytical questions along with theory

CSIR NET Life Science Topic-Wise Question Analysis 

The previous six papers indicate that some subjects receive more questions than others. Candidates should prioritise these areas during revision.

Across all six papers, Molecular Biology, Cell Biology, Ecology and Evolution, and Genetics consistently contribute the highest number of questions, making them priority revision areas.

Most Repeated Concepts in CSIR NET Life Science 

Several concepts appeared repeatedly across nearly every paper, indicating their continued importance in the examination. Candidates should revise these topics thoroughly before the examination. Below are the CSIR NET Life Science Repeated Concepts

DNA Replication Machinery

DNA replication remains one of the most repeated topics. Questions frequently ask candidates to match bacterial replication proteins with their eukaryotic counterparts.

Rolling-circle replication and the role of PCNA also appear repeatedly.

Translation Initiation

Translation initiation factors are another recurring area. Questions commonly test the functions of IF-1, IF-2, IF-3, eIF2, eIF2B, eIF4G, and eIF6. Upstream open reading frames (uORFs) and tmRNA-mediated ribosome rescue also appear in several papers.

Cell Signalling

GPCR signalling, second messengers, and monomeric G-proteins remain high-frequency topics.

Common concepts include:

• GAP inactivates G-proteins.

• GEF activates G-proteins.

• Ran-GAP is located in the cytosol.

• Ran-GEF is located in the nucleus.

Cell Cycle Regulation

Questions regularly focus on the roles of Cdc2/Cdk1, Cdc25, Wee1, CAK, and Sic1. Candidates should clearly understand how these proteins regulate mitotic entry.

Developmental Biology

Developmental Biology repeatedly includes model-organism experiments.

Commonly tested topics include:

• Drosophila segmentation gene hierarchy

• Spemann Organizer

• Nieuwkoop centre

• C. elegans blastomere specification

• Blastema-mediated regeneration

Plant Sciences

Plant hormone biosynthesis and signalling are tested regularly.

Frequently repeated topics include:

• ABA biosynthesis

• Ethylene biosynthesis

• Cytokinin signalling

• C3, C4, and CAM pathways

• PEPCase activity

Ecology and Evolution

Population genetics and ecological calculations appear consistently.

Candidates should practise:

• Hardy-Weinberg equilibrium

• Logistic population growth

• Species diversity indices

• r-selected and K-selected species

Immunology

Repeated concepts include:

• MHC Class I and MHC Class II

• Complement system

• T-dependent and T-independent antigens

• Adaptive immune responses

CSIR NET Life Science Most Repeated Questions 

These CSIR NET Life Science Frequently Asked Questions are based on concepts that have appeared repeatedly in the previous six examination papers.

Molecular Biology

Q. What is the function of PCNA in eukaryotic replication?
Answer: It acts as a sliding clamp and increases DNA polymerase processivity.

Q. RNA polymerase II in eukaryotes requires which factor to initiate transcription?
Answer: TFIIB and other general transcription factors.

Q. Which enzyme unwinds DNA immediately ahead of the replication fork?
Answer: Helicase.

Q. What tags a truncated or defective mRNA for ribosome rescue?
Answer: tmRNA.

Cell Biology

Q. What converts a GTP-bound active G-protein to its inactive GDP-bound state?
Answer: GAP (GTPase Activating Protein).

Q. Where is Ran-GAP localized in the cell?
Answer: Cytosol.

Q. What phosphatase removes the inhibitory phosphate to activate Cdk1 for mitotic entry?
Answer: Cdc25.

Q. What does FRAP measure?
Answer: Fluorescence Recovery After Photobleaching measures protein mobility in membranes.

Developmental Biology

Q. What is the correct order of Drosophila segmentation gene activity?
Answer: Maternal → Gap → Pair-rule → Segment polarity.

Q. What is the default fate of amphibian ectoderm in the absence of BMP signalling?
Answer: Neural tissue.

Q. What do Chordin, Noggin, and Goosecoid do?
Answer: They antagonize BMP signalling.

Q. What is the origin of Nieuwkoop centre cells?
Answer: Vegetal/endodermal.

Plant Sciences

Q. Which enzyme catalyses the final step of ethylene biosynthesis?
Answer: ACC oxidase.

Q. In two-component signalling, where does autophosphorylation occur?
Answer: On a histidine residue in the transmitter domain.

Q. When is PEPCase active in C4 and CAM plants?
Answer: C4 during the day and CAM during the night.

Q. What is the dark reversion of phytochrome?
Answer: Conversion of Pfr back to Pr in darkness.

Ecology and Evolution

Q. At what population size is the logistic growth rate maximised?
Answer: N = K/2.

Q. What conditions are required for Hardy-Weinberg equilibrium?
Answer: Large population, random mating, no selection, no migration, and no mutation.

Q. What is character displacement?
Answer: Evolution of divergent traits that reduces niche overlap.

Q. What best explains the evolution of monogamy?
Answer: Mate guarding, scattered mates, or the need for biparental care.

Genetics

Q. How can linked genes be identified in a dihybrid cross?
Answer: Compare the observed F₂ ratio with the expected 9:3:3:1 ratio.

Q. What is the key feature of Recombinant Inbred Lines (RILs)?
Answer: They are true-breeding populations produced through repeated inbreeding.

Q. What is the difference between penetrance and expressivity?
Answer: Penetrance is the percentage of individuals showing a phenotype, while expressivity describes the degree of phenotype expression.

Immunology

Q. Why are polysaccharide antigens considered T-independent?
Answer: They activate B cells without helper T-cell involvement.

Q. What is the function of the mannose-6-phosphate (M6P) tag?
Answer: It directs proteins from the Golgi apparatus to lysosomes.

CSIR NET Life Science Repeated PYQ Question Patterns 

CSIR NET Life Science Important PYQs show that certain question formats appear regularly, even when the biological topic changes. Candidates should practise these formats along with conceptual revision.

Among these, statement-combination questions remain the most common format in Part C. Eliminating one incorrect statement often helps narrow down the correct option.

Topics to Prioritise Before the CSIR NET Life Sciences Exam 

During the final phase of preparation, candidates should prioritise the following areas: 

1. Experimental reasoning using gels, blots, pedigrees, and enzyme kinetics.

2. Molecular Biology, especially replication, transcription, and translation.

3. Cell signalling pathways and vesicular transport.

4. Cell cycle regulation and checkpoint proteins.

5. Developmental Biology model organisms.

6. Population genetics and ecological calculations.

7. Plant hormone biosynthesis and photosynthesis pathways.

8. Immunology concepts related to MHC and adaptive immunity.

9. Genetics, including linkage mapping and pedigree analysis.

10. General Aptitude questions from Part A.

The CSIR NET Life Science Most Repeated Questions provide a clear picture of the concepts that receive consistent attention in the examination. The six-paper analysis shows that Molecular Biology, Cell Biology, Ecology and Evolution, and Genetics remain the highest-weightage subjects. It also highlights the growing importance of experimental reasoning and statement-based questions.

Candidates should revise recurring concepts, practise experimental and statement-based questions, and strengthen conceptual understanding across all major subjects. Regular practice of previous years' papers can improve accuracy, speed, and confidence while helping candidates recognise familiar question patterns. A focused preparation strategy based on the CSIR NET Life Science Most Repeated Questions can make revision more organised and effective.