- A two-celled embryo is made of blastomeres A and B. If the two blastomeres are experimentally separated, the ‘A’ blastomere generates all the cells it would normally
make. However, the ‘B’ blastomere in isolation makes only a small fraction of cells it would normally make. Based on the above observations only, which one of the following conclusions is correct?
(1) ‘A’ blastomeres is autonomously specified while ‘B’ blastomere is conditionally specified
(2) ‘A’ blastomeres is conditionally specified while ‘B’ blastomere is autonomously specified
(3) Descendants of ‘A’ blastomeres are autonomously specified
(4) Descendants of ‘B’ blastomeres can either be autonomously specified or conditionally
specified.In the 2-celled stage of Caenorhabditis elegans embryonic development, experimental separation of the blastomeres reveals key insights into their modes of cell fate specification. The P1 blastomere, when isolated, can generate all the cell types it normally produces, indicating that its development is autonomously specified. This means intrinsic factors within P1 largely determine its fate without reliance on external cues.
Conversely, the AB blastomere, when isolated, can produce only a subset of the cell types it usually would, indicating that its specification is conditional. This dependency on spatial context or interactions with other cells, such as descendants of P1 and P2 cells, underscores a regulative developmental pattern where fate determination depends on extrinsic factors.
Key conclusions include:
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(A) P1 blastomere exhibits autonomous specification.
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(C) AB blastomere shows conditional specification.
Statements (B) and (D) are inconsistent with the experimental observations.
Therefore, the correct combination is:
(1) A and C
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1 Comment
Muskan Yadav
December 7, 2025(A) P1 blastomere exhibits autonomous specification.
(C) AB blastomere shows conditional specification.