- The following figure represents the interaction between different blastomeres in a 4-cell stage of C. elegans embryo:
The following statements were made regarding the above:
A. The fate of EMS blastomere is autonomously specified.
B. The default fate of EMS blastomere is MS cell lineage.
C. Conditional specification can be observed in the development of E cell lineage.
D. Assuming that a receptor needs to be activated for E fate, a C. elegans embryo where the receptor is constitutively active, is likely to develop cells of E fate only, in all three of the above cases.
Which one of the following options represents the combination of all correct statements?
(1) A and C only (2) B and C only
(3) A, B and C (4) B, C and D
During early embryonic development in Caenorhabditis elegans, the EMS blastomere plays a pivotal role by giving rise to two distinct lineages: the MS (mesoderm) and the E (endoderm) cell lineages. The fate of EMS is a classic example of conditional specification, where cell fate is not intrinsic but determined by intercellular signaling and gene regulatory networks.
Statement A is incorrect because the EMS blastomere’s fate is not autonomously specified; rather, it needs inductive signals from the neighboring P2 cell to specify the E cell lineage.
Statement B is correct; the EMS blastomere’s default fate is the MS lineage. In the absence of P2 signals, EMS division produces two MS cells, and no endoderm (E cells) is formed.
Statement C is accurate. The development of the E cell lineage is conditionally specified, requiring P2 signaling via pathways such as the Wnt signaling cascade to induce this fate.
Statement D is also true. If the receptor required for E cell fate induction is constitutively active, EMS cells will specify as E lineage cells irrespective of P2 signals, leading to all EMS daughters adopting E fate.
In summary, the precise combination of correct statements is:
(4) B, C and D
1 Comment
Muskan Yadav
December 7, 2025B, C and D is the right statement.