Q.19 Which of the following is NOT a characteristic morphological feature of
apoptotic cells?
(A) Disassembly of nuclear envelope
(B) DNA fragmentation
(C) Increased cell size
(D) Membrane blebbing
Answer: (C) Increased cell size
Apoptotic cells exhibit distinct morphological changes driven by programmed cell death pathways, including caspase activation. Option (C) is incorrect for apoptosis, as cells shrink rather than enlarge. This question tests key differences between apoptosis and necrosis for CSIR NET Life Sciences preparation.
Option Analysis
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(A) Disassembly of nuclear envelope: Caspases degrade nuclear lamina and envelope components during late apoptosis stages, leading to nuclear breakdown.
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(B) DNA fragmentation: A hallmark feature where internucleosomal cleavage by CAD/DFF40 produces 180-200 bp fragments, visible as laddering on gels.
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(C) Increased cell size: Not characteristic; apoptotic cells undergo shrinkage (pyknosis) due to ion efflux and cytoskeleton changes, unlike necrosis swelling.
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(D) Membrane blebbing: Results from ROCK I activation post-caspase cleavage, forming protrusions that detach as apoptotic bodies while maintaining membrane integrity.
Apoptosis, or programmed cell death, shows specific characteristic morphological features of apoptotic cells like shrinkage and blebbing, vital for CSIR NET Life Sciences. Identifying what is NOT a characteristic morphological feature of apoptotic cells—such as increased cell size—helps distinguish it from necrosis.
Key Morphological Features
Apoptotic cells display:
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Cell shrinkage with dense eosinophilic cytoplasm.
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Chromatin condensation (pyknosis) and nuclear fragmentation.
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Membrane blebbing leading to apoptotic bodies.
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Nuclear envelope disassembly in late stages via caspase action.
Why Increased Cell Size is NOT Characteristic
Increased cell size signals necrosis, not apoptosis. Apoptotic volume decrease (AVD) occurs via K+ efflux and caspase-mediated cytoskeleton disassembly, shrinking cells. Necrotic cells swell due to organelle damage and membrane rupture.
| Feature | Apoptosis | Necrosis |
|---|---|---|
| Cell Size | Shrinkage | Increased/swelling |
| DNA Changes | Fragmentation | Karyolysis/smear |
| Membrane | Blebbing, intact | Rupture |
| Nuclear Envelope | Disassembly (late) | Dilatation |
| Inflammation | Absent | Present |
Exam Relevance for CSIR NET
Mastering characteristic morphological feature of apoptotic cells aids in questions on cell death pathways, relevant to molecular biology and biotechnology units. DNA fragmentation and blebbing confirm apoptosis biochemically and morphologically.
