CSIR NET LIFESCIENCE FREQUENTLY ASKED QUESTIONS WITH ANSWERS (2 MARKS)

 

1. What is the function of DNA polymerase I in E. coli replication?

It removes RNA primers using 5′→3′ exonuclease activity and fills gaps with DNA.

2. Which step of translation requires GTP hydrolysis by EF-Tu in prokaryotes?

Binding of aminoacyl-tRNA to the A site of the ribosome

3. In the lac operon, what happens when glucose and lactose are both present?

Catabolite repression prevents lac operon transcription (low cAMP → CAP inactive).

4. What does a Lineweaver–Burk plot show for competitive inhibition?

Lines intersect on the Y-axis; $V_{max}$ unchanged, $K_m$ increases.

5. Which checkpoint ensures all chromosomes are properly attached to spindle fibers?

The spindle assembly checkpoint (metaphase–anaphase transition).

6. What is the second messenger produced by phospholipase C activity?

IP₃ and DAG (from PIP₂ hydrolysis).

7. Where does the Calvin cycle occur in C₃ plants?

In the stroma of chloroplasts.

8. What is the function of primers in PCR?

They provide free 3′-OH groups for DNA polymerase to initiate synthesis.

9. What type of chromatin is transcriptionally active?

Euchromatin.

10. What is the main function of peroxisomes?

Breakdown of hydrogen peroxide and long-chain fatty acids (β-oxidation).

11. What does a recombination frequency of 50% indicate?

Independent assortment; genes are unlinked or on different chromosomes.

12. Which antibody is present in highest concentration in blood plasma?

IgG.

13. What is the function of restriction endonucleases?

They cut DNA at specific palindromic sequences.

14. What is the role of the organizer region in amphibian embryos?

It induces dorsal axis formation (Spemann’s organizer).

15. What type of selection maintains stable polymorphism?

Balancing (heterozygote advantage) selection.

16. What is the Shannon diversity index used to measure?

Species diversity considering richness and evenness.

17. What triggers stomatal opening?

Blue light activates H⁺-ATPase, leading to K⁺ uptake and turgor increase in guard cells.

18. What hormone regulates water reabsorption in kidneys?

Antidiuretic hormone (ADH / vasopressin).

19. What does a p-value < 0.05 indicate?

The result is statistically significant at the 5% level.

20. What is the purpose of SDS in SDS-PAGE?

It denatures proteins and gives them uniform negative charge proportional to size.