Q98. Match the types of cell movements during gastrulation in Column I with the description in Column II
| Column I | Column II |
|---|---|
| P. Invagination | (i) Migration of individual cells from the surface |
| Q. Involution | (ii) Folding of a sheet (epithelium) of cells |
| R. Regression | (iii) Splitting of one cell sheet into two layers |
| S. Delamination | (iv) Parallel sheets of an expanding outer layer of cells so that spreads over the internal surface of |
(A) P–(ii), Q–(iii), R–(iv), S–(i)
(B) P–(iv), Q–(i), R–(iii), S–(ii)
(C) P–(ii), Q–(iv), R–(i), S–(iii)
(D) P–(iii), Q–(ii), R–(iv), S–(i)
The correct answer is (C) P-(ii), Q-(iv), R-(i), S-(iii).
Gastrulation involves specific cell movements that reorganize the blastula into germ layers. Each term in Column I matches a unique description in Column II based on standard definitions from developmental biology.
Column II Definitions
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(i) Migration of individual cells from the surface: Describes cells detaching from the epiblast or surface layer and moving inward individually, often as mesenchymal cells. This aligns with ingression but fits “regression” in contexts like primitive streak regression, where mesodermal cells migrate away from the streak surface.
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(ii) Folding of a sheet (epithelium) of cells: Refers to invagination, where an epithelial layer bends inward, like poking a soft ball, forming structures such as the blastopore lip.
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(iii) Splitting of one cell sheet into two layers: Defines delamination, where a single cell layer separates into two parallel sheets, seen in hypoblast formation or certain endoderm layers.
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(iv) Parallel sheets of an expanding outer layer of cells so that spreads over the internal surface: Though phrasing is incomplete, this matches involution, where the outer expanding layer rolls inward (like a tank tread) to line the inner surface, common in frog and chick gastrulation.
Option Analysis
| Option | P | Q | R | S | Correct Matches |
|---|---|---|---|---|---|
| (A) | (ii) ✓ | (iii) ✗ | (iv) ✗ | (i) ✗ | Only P correct |
| (B) | (iv) ✗ | (i) ✗ | (iii) ✗ | (ii) ✗ | None correct |
| (C) | (ii) ✓ | (iv) ✓ | (i) ✓ | (iii) ✓ | All correct |
| (D) | (iii) ✗ | (ii) ✗ | (iv) ✗ | (i) ✗ | None correct |
Gastrulation represents a pivotal phase in embryonic development, where cell movements during gastrulation transform the single-layered blastula into a tri-layered gastrula comprising ectoderm, mesoderm, and endoderm. For CSIR NET Life Sciences aspirants, understanding types of cell movements during gastrulation—such as invagination, involution, regression, and delamination—is crucial, especially for matching questions like Q98. This SEO-optimized guide decodes these movements, solves Q98 step-by-step, and provides exam-focused insights to boost your preparation in developmental biology.
What Are Cell Movements During Gastrulation?
Gastrulation orchestrates five primary cell movements during gastrulation: invagination, involution, ingression, delamination, and epiboly. These morphogenetic processes involve changes in cell shape, adhesion, and migration, driven by signals like FGF, Wnt, and Nodal. In frogs, the dorsal lip initiates these via blastopore formation; in chicks, the primitive streak serves a similar role. Regression specifically denotes mesodermal cell migration post-involution from the regressing streak.
Detailed Definitions of Key Movements
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Invagination (P): Folding of an epithelial sheet inward, forming a pouch like the blastopore. Driven by apical constriction. Matches (ii).
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Involution (Q): Inward rolling of an expanding outer layer to spread over internal surfaces, akin to a conveyor belt. Key in mesendoderm internalization. Matches (iv).
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Regression (R): Individual cell migration from the surface (primitive streak), spreading laterally as mesoderm. Linked to streak regression and chemo-repulsion by FGF8. Matches (i).
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Delamination (S): Cleavage of one cell sheet into two parallel layers, forming epiblast-hypoblast in chicks. Matches (iii).
Matching Column I with Column II
Column I (Types) matches Column II (Descriptions) as: P-(ii), Q-(iv), R-(i), S-(iii)—Option C. This aligns with standard texts like Gilbert’s Developmental Biology. Other options fail: (A) mismatches Q/R/S; (B)/(D) invert core definitions.
Exam Tips for CSIR NET
Focus on amphibian/chick models: frog uses involution at blastopore; chick features primitive streak regression. Practice PYQs on morphogenetic movements—80% weightage.
