Kerala Brain‑Eating Amoeba — Simple Guide & Precautions

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Kerala Brain‑Eating Amoeba — Simple Guide

Short, clear advice about Naegleria fowleri, symptoms, and easy precautions.

What is it?

Naegleria fowleri is a tiny amoeba found in warm freshwater. It can enter the body through the nose and cause a rare brain infection called PAM. Infections are very rare but serious.

Found in: Warm lakes, rivers, ponds, hot springs, and poorly maintained pools.

Symptoms (watch closely)

• Severe headache and high fever
• Nausea, vomiting, stiff neck
• Light sensitivity, confusion, seizures

If symptoms appear within 1–14 days after freshwater exposure, get emergency care and tell doctors about the water contact.

Quick Precautions — Easy Steps

1. Avoid warm, stagnant water

Skip shallow, warm ponds and unchlorinated pools.

2. Keep water out of your nose

Use a nose clip or avoid submerging your head.

3. Use safe water for nasal rinsing

Only boiled (cooled) or distilled water for neti pots.

4. Prefer chlorinated pools

Public pools with good maintenance are safer.

Compact Flowchart

A small visual guide you can save or share.

Remember

The infection is very rare. Simple steps like not letting water go up your nose and using safe water for nasal cleaning reduce risk a lot. Stay calm and be careful.

This page is for awareness only and not medical advice. For emergencies, contact local health services.

50-Question Biochemistry Quiz Try to Solve it............

50-Question Biochemistry Quiz

Answer all questions below and submit to see final results and download scorecard PDF.

Made for study & practice — edit questions freely.

Biotechnology PCR MCQ Quiz Series

🧬 Biotechnology PCR MCQ Quiz Series

Welcome to the CSIR-NET/GATE Level Quiz Series on Polymerase Chain Reaction (PCR).
Attempt quizzes step by step and test your preparation.

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🔥 Best of luck with your CSIR NET / GATE exam preparation!
Attempt all quizzes to strengthen your PCR knowledge.

Polymerase Chain Reaction (PCR) Quiz – Part 5 (Advanced Variants & Troubleshooting)

Attempt all 10 questions. Click Submit to check your score and correct answers.

41. Which PCR variant is BEST suited for quantifying mRNA expression levels?

a) Nested PCR
b) RT-qPCR
c) Digital PCR
d) Hot-start PCR

42. A PCR reaction shows multiple nonspecific bands. Which adjustment is MOST helpful?

a) Lowering annealing temperature
b) Increasing primer concentration
c) Increasing annealing temperature
d) Decreasing Mg²⁺ concentration

43. Which PCR method is MOST suitable for detecting rare alleles in a heterogeneous population?

a) Touchdown PCR
b) Digital PCR
c) Multiplex PCR
d) Gradient PCR

44. In case of primer-dimer formation, which modification is MOST effective?

a) Reduce template concentration
b) Increase extension time
c) Redesign primers
d) Add more Mg²⁺ ions

45. Which PCR variant is MOST useful for detecting viral load in patients?

a) Nested PCR
b) RT-qPCR
c) Digital PCR
d) Hot-start PCR

46. Which of the following is a common cause of PCR failure?

a) Incorrect primer design
b) Absence of Mg²⁺ ions
c) Poor template quality
d) All of the above

47. Which modification in PCR helps to reduce contamination issues?

a) Hot-start PCR
b) Nested PCR
c) Use of uracil-DNA glycosylase (UDG)
d) Touchdown PCR

48. Which PCR technique is MOST used for single-cell analysis?

a) Digital PCR
b) Multiplex PCR
c) RT-PCR
d) Gradient PCR

49. Which step would you modify to increase yield without affecting specificity?

a) Increase cycle number
b) Decrease extension time
c) Reduce primer length
d) Increase annealing temperature

50. Which advanced PCR technique allows absolute quantification without reference standards?

a) qPCR
b) Digital PCR
c) RT-PCR
d) Hot-start PCR

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Polymerase Chain Reaction (PCR) Quiz – Part 4: Numerical & Analytical Questions

Attempt all 10 questions. Click Submit to check your score and correct answers.

31. Which factor MOST affects PCR specificity?

a) dNTP concentration
b) Annealing temperature
c) Polymerase concentration
d) Buffer pH

32. Hot-start PCR prevents:

a) Primer degradation
b) Nonspecific amplification
c) Template denaturation
d) Enzyme inactivation

33. Which additive is often used to improve PCR amplification of GC-rich templates?

a) Glycerol
b) DMSO
c) NaCl
d) EDTA

34. Which enzyme is commonly used for high-fidelity PCR?

a) Taq polymerase
b) Pfu polymerase
c) Reverse transcriptase
d) DNA ligase

35. Which PCR type is BEST suited for identifying rare mutations in a sample?

a) Nested PCR
b) qPCR
c) Digital PCR
d) Multiplex PCR

36. Which PCR technique allows amplification without thermal cycling?

a) LAMP (Loop-mediated isothermal amplification)
b) Touchdown PCR
c) Nested PCR
d) Hot-start PCR

37. Which application commonly uses reverse transcriptase PCR?

a) Gene expression studies
b) DNA fingerprinting
c) Protein purification
d) Plasmid cloning

38. Which PCR method allows simultaneous detection of multiple pathogens?

a) Nested PCR
b) Multiplex PCR
c) Hot-start PCR
d) Digital PCR

39. Which step in PCR is MOST heat-sensitive?

a) Denaturation
b) Annealing
c) Extension
d) Template storage

40. Which variant of PCR is widely used in next-generation sequencing (NGS) library preparation?

a) qPCR
b) Bridge PCR
c) Nested PCR
d) Allele-specific PCR

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Polymerase Chain Reaction (PCR) Quiz – Part 3: Quantitative & Real-Time PCR

Attempt all 10 questions. Click Submit to check your score and correct answers.

21. The annealing temperature in PCR is usually:

a) 20–30°C
b) 50–65°C
c) 90–95°C
d) 100°C

22. The extension step of PCR using Taq polymerase typically occurs at:

a) 37°C
b) 50°C
c) 72°C
d) 95°C

23. The purpose of magnesium ions (Mg²⁺) in PCR is to:

a) Stabilize DNA duplex
b) Act as a cofactor for DNA polymerase
c) Denature DNA
d) Inhibit nonspecific binding

24. Which parameter is MOST critical for primer design?

a) Primer length
b) GC content
c) Melting temperature (Tm)
d) All of the above

25. In qPCR, the cycle threshold (Ct) value is:

a) The number of cycles where amplification starts
b) The number of cycles at which fluorescence exceeds background
c) Always 40 cycles
d) The melting point of primers

26. A lower Ct value in qPCR indicates:

a) Lower template concentration
b) Higher template concentration
c) Primer dimer formation
d) Failed amplification

27. Which method in qPCR uses fluorescent probes specific to the target sequence?

a) SYBR Green method
b) TaqMan assay
c) Gel electrophoresis
d) Southern blot

28. The efficiency of PCR amplification ideally should be:

a) 50%
b) 75%
c) 90–110%
d) 200%

29. Which plot is used in qPCR to determine amplification efficiency?

a) Melt curve
b) Standard curve
c) Growth curve
d) Calibration curve

30. Melt curve analysis in qPCR helps to:

a) Confirm specificity of amplification
b) Determine Mg²⁺ concentration
c) Measure extension rate
d) Quantify template directly

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Polymerase Chain Reaction (PCR) Quiz – Part 2: Techniques & Applications

Attempt all 10 questions. Click Submit to check your score and correct answers.

11. Which PCR variant is used for amplifying RNA templates?

a) Nested PCR
b) RT-PCR
c) qPCR
d) Hot-start PCR

12. Which of the following applications uses PCR?

a) Forensic DNA profiling
b) Gene cloning
c) Pathogen detection
d) All of the above

13. Nested PCR improves specificity by:

a) Using two sets of primers in successive runs
b) Using degenerate primers
c) Increasing Mg²⁺ concentration
d) Reducing annealing temperature

14. Real-time PCR monitors amplification by measuring:

a) Radioactive isotopes
b) Absorbance
c) Fluorescence
d) Enzyme activity

15. Which dye binds to double-stranded DNA in qPCR?

a) SYBR Green
b) Coomassie Blue
c) Safranin
d) Crystal violet

16. Which PCR variant is best for detecting a single nucleotide polymorphism (SNP)?

a) Allele-specific PCR
b) RT-PCR
c) Nested PCR
d) Touchdown PCR

17. Which PCR modification reduces nonspecific amplification by gradually lowering the annealing temperature?

a) Hot-start PCR
b) Touchdown PCR
c) Digital PCR
d) Multiplex PCR

18. Multiplex PCR allows:

a) Amplification of multiple targets in one reaction
b) Amplification of a single target with multiple enzymes
c) Extension without primers
d) DNA sequencing

19. Which of the following is NOT an application of PCR?

a) Gene expression analysis
b) DNA fingerprinting
c) Protein purification
d) Detection of pathogens

20. Digital PCR is mainly used for:

a) High-throughput sequencing
b) Absolute quantification of DNA
c) Gene cloning
d) Protein expression

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“PCR Quiz Part 1 – Basics of Polymerase Chain Reaction (10 MCQs)”

Attempt all 10 questions. Click Submit to check your score and correct answers.

1. The melting temperature (Tm) of a DNA duplex depends on its GC content. Which formula is commonly used for short primers?

a) Tm = 2(A+T) + 4(G+C)
b) Tm = (A+T+G+C) × 2
c) Tm = 4(A+T) + 2(G+C)
d) Tm = (G+C)/(A+T) × 100

2. A PCR reaction starts with 100 copies of DNA. After 20 cycles (100% efficiency), how many copies will be produced?

a) 1.05 × 10⁶
b) 1.05 × 10⁸
c) 1.05 × 10⁷
d) 1.05 × 10⁹

3. In PCR, the denaturation step is usually carried out at:

a) 37°C
b) 55°C
c) 72°C
d) 94°C

4. Which DNA polymerase is commonly used in standard PCR?

a) DNA Pol I
b) DNA Pol III
c) Taq polymerase
d) Reverse transcriptase

5. Which of the following is NOT essential for PCR?

a) DNA template
b) dNTPs
c) Restriction enzyme
d) Primers

6. What is the typical length of primers used in PCR?

a) 6–10 bases
b) 18–24 bases
c) 40–60 bases
d) >100 bases

7. If extension rate of Taq polymerase is ~1000 bases/min, how long is required to amplify a 2 kb fragment?

a) 30 sec
b) 1 min
c) 2 min
d) 3 min

8. The exponential phase of PCR continues until:

a) Primers run out
b) dNTPs run out
c) Polymerase loses activity
d) All of the above

9. Hot-start PCR is mainly used to:

a) Increase DNA denaturation
b) Prevent nonspecific amplification
c) Increase speed of polymerase
d) Replace annealing step

10. Which of the following is a limitation of Taq polymerase?

a) Low fidelity (no proofreading)
b) Works only at 25°C
c) Cannot use primers
d) Requires Mg²⁺ ions

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Cell Cycle and Its Regulation

Introduction

The cell cycle is a fundamental process through which cells grow, duplicate their genetic material, and divide into two daughter cells. It ensures genetic stability and proper cell proliferation, which is critical for development, tissue repair, and reproduction. Dysregulation of the cell cycle is closely associated with diseases such as cancer.

Phases of the Cell Cycle

The cell cycle is broadly divided into two main stages: Interphase and M phase (Mitosis + Cytokinesis).

1.     Interphase (90% of cycle duration)

o    G1 phase (Gap 1): Cell grows, accumulates nutrients, synthesizes RNA and proteins.

o    S phase (Synthesis): DNA replication occurs; histone proteins are synthesized.

o    G2 phase (Gap 2): Preparation for mitosis; cell checks for DNA damage and ensures all DNA is replicated.

2.     M phase (Mitosis + Cytokinesis)

o    Prophase → Prometaphase → Metaphase → Anaphase → Telophase.

o    Followed by Cytokinesis: division of cytoplasm into two daughter cells.

3.     G0 Phase (Quiescent state)

o    Non-dividing, resting phase. Cells like neurons remain in G0 permanently.

Checkpoints in Cell Cycle Regulation

Checkpoints are surveillance mechanisms that ensure fidelity of cell division:

Checkpoint	Controlled By	Function
G1/S Checkpoint (Restriction Point)	Cyclin D–Cdk4/6, Rb–E2F pathway	Ensures DNA integrity before replication begins
S-phase Checkpoint	ATR/Chk1 pathway	Monitors ongoing DNA replication and repair
G2/M Checkpoint	Cyclin B–Cdk1 (MPF), p53, Wee1/Myt1	Ensures DNA is fully replicated and undamaged before mitosis
Spindle Assembly Checkpoint (SAC)	APC/C, Mad2, Bub proteins	Ensures proper attachment of chromosomes to spindle before anaphase

 

Key Regulators of Cell Cycle

1.     Cyclins and Cyclin-Dependent Kinases (Cdks):

o    Cdks are serine/threonine kinases activated by binding to cyclins.

o    Different cyclin–Cdk complexes drive progression through each phase.

Phase	Cyclin–Cdk Complex
G1 → S	Cyclin D–Cdk4/6, Cyclin E–Cdk2
S → G2	Cyclin A–Cdk2
G2 → M	Cyclin B–Cdk1 (Maturation Promoting Factor, MPF)

2.     Cdk Inhibitors (CKIs):

o    Two families:

§  INK4 family (p15, p16, p18, p19) → specifically inhibit Cdk4/6.

§  Cip/Kip family (p21, p27, p57) → broadly inhibit cyclin–Cdk complexes.

3.     Retinoblastoma Protein (Rb):

o    Acts as a brake in G1 phase by binding E2F transcription factors.

o    Cyclin Cdk phosphorylation of Rb releases E2F, allowing S-phase entry.

4.     p53 (Guardian of Genome):

o    Responds to DNA damage by activating p21 (a CKI), which halts the cell cycle.

o    If damage is irreparable, p53 triggers apoptosis.

5.     Anaphase-Promoting Complex (APC/C):

o    A ubiquitin ligase that degrades securin and cyclins.

o    Ensures progression from metaphase to anaphase and mitotic exit.

Cell Cycle Regulation and Cancer

• In cancer, cell cycle checkpoints are often defective.
• Overactive cyclins (e.g., Cyclin D1 amplification) or loss of CKIs (like p16 deletion) drive uncontrolled proliferation.
• Mutations in p53 or Rb are common hallmarks in many cancers.
• Thus, targeting cell cycle regulators is an important therapeutic strategy (e.g., Cdk4/6 inhibitors like Palbociclib).

Conclusion

The cell cycle is a highly ordered and tightly regulated process involving cyclins, Cdks, CKIs, and checkpoint proteins. Its regulation maintains genomic stability, while its dysregulation leads to uncontrolled cell growth and cancer. Understanding these mechanisms is not only central to developmental biology but also provides a foundation for targeted cancer therapies, making it a vital area for CSIR-NET preparation.

📖 Reference Books for CSIR-NET:

• Alberts et al., Molecular Biology of the Cell
• Lodish et al., Molecular Cell Biology
• Bruce Alberts’ figures for visual understanding

MCQs on Cell Cycle and Regulation

1.Which of the following cyclin–Cdk complexes is required for the G2 → M transition?

a) Cyclin D–Cdk4/6
b) Cyclin E–Cdk2
c) Cyclin A–Cdk2
d) Cyclin B–Cdk1

Answer: d) Cyclin B–Cdk1
Explanation: The Cyclin B–Cdk1 complex, also called Maturation Promoting Factor (MPF), is essential for entry into mitosis.

2.The restriction point (R-point) in mammalian cells is regulated mainly by:

a) Cyclin A–Cdk2
b) Cyclin D–Cdk4/6 and Rb–E2F pathway
c) Cyclin B–Cdk1
d) p53 and p21

Answer: b) Cyclin D–Cdk4/6 and Rb–E2F pathway
Explanation: In G1, phosphorylation of Rb by Cyclin D–Cdk4/6 releases E2F transcription factor, allowing the cell to pass the restriction point and enter S-phase.

3.Which checkpoint ensures that all chromosomes are properly attached to the spindle before separation?

a) G1/S checkpoint
b) G2/M checkpoint
c) Spindle Assembly Checkpoint (SAC)
d) DNA replication checkpoint

Answer: c) Spindle Assembly Checkpoint (SAC)
Explanation: SAC monitors kinetochore–microtubule attachment and delays anaphase onset until proper alignment is achieved.

4.The INK4 family of Cdk inhibitors (CKIs) specifically inhibits:

a) Cdk1
b) Cdk2
c) Cdk4 and Cdk6
d) Cdk5

Answer: c) Cdk4 and Cdk6
Explanation: INK4 proteins (p15, p16, p18, p19) prevent Cyclin D from activating Cdk4/6, blocking progression through G1.

5.Which protein is known as the “Guardian of the Genome”?

a) Rb
b) E2F
c) p53
d) APC/C

Answer: c) p53
Explanation: p53 prevents the propagation of damaged DNA by halting the cell cycle (via p21) or inducing apoptosis.

6.The Anaphase-Promoting Complex (APC/C) primarily functions as:

a) A serine/threonine kinase
b) A ubiquitin ligase complex
c) A DNA helicase
d) A transcription factor

Answer: b) A ubiquitin ligase complex
Explanation: APC/C marks securin and cyclins for degradation, allowing sister chromatid separation and mitotic exit.

7.Which of the following occurs only during S phase?

a) Chromosome condensation
b) DNA replication and histone synthesis
c) Centrosome duplication and spindle assembly
d) Cytokinesis

Answer: b) DNA replication and histone synthesis
Explanation: DNA duplication along with synthesis of histones occurs in S phase to package the replicated DNA.

8.Loss-of-function mutation in Rb protein leads to:

a) Arrest at G0 phase
b) Continuous release of E2F and uncontrolled cell cycle entry
c) Inhibition of Cyclin D–Cdk4 activity
d) Activation of p53 pathway

Answer: b) Continuous release of E2F and uncontrolled cell cycle entry
Explanation: Rb normally restrains E2F. Without functional Rb, cells bypass G1 checkpoint and proliferate uncontrollably.

9.Which of the following drugs is a Cdk4/6 inhibitor used in cancer therapy?

a) Taxol
b) Cisplatin
c) Palbociclib
d) Colchicine

Answer: c) Palbociclib
Explanation: Palbociclib inhibits Cyclin D–Cdk4/6, preventing Rb phosphorylation and blocking cell cycle progression in cancers.

10.Which kinase is involved in DNA damage response by activating Chk1/Chk2 pathway?

a) ATM/ATR
b) APC/C
c) Cdk5
d) Wee1

Answer: a) ATM/ATR
Explanation: ATM responds to double-strand breaks, ATR to replication stress, both activating Chk1/Chk2 to halt the cycle.

Cell Cycle Checkpoints – Quick Revision

Checkpoint	Phase	Key Regulators	Main Function
G1/S (Restriction Point)	End of G1	Cyclin D–Cdk4/6, Rb–E2F, p53–p21	Ensures cell has sufficient nutrients, growth factors, and no DNA damage before DNA replication.
S-phase checkpoint	During S	ATR, Chk1, Cdc25	Monitors DNA replication stress, prevents collapsed replication forks.
G2/M checkpoint	End of G2	Cyclin B–Cdk1 (MPF), Wee1 kinase, Cdc25 phosphatase, p53	Ensures DNA replication is complete and DNA damage is repaired before mitosis.
Spindle Assembly Checkpoint (SAC)	Metaphase–Anaphase	APC/C, Mad2, Bub proteins, securin–separase	Ensures all chromosomes are properly attached to spindle microtubules before chromatid separation.
DNA Damage checkpoint	Throughout	ATM, ATR, Chk1/Chk2, p53	Detects DNA breaks and halts cycle for repair or induces apoptosis if damage is severe.

Key Mnemonic:

• G1/S → Growth & nutrients check
• S → DNA replication fidelity
• G2/M → DNA repair before mitosis
• SAC → Chromosome alignment check