During the early cleavage stages of Caenorhabditis elegans embryonic development, the zygote divides asymmetrically to produce two blastomeres: the anterior AB cell and the posterior P1 cell. Experimental studies where individual blastomeres are separated reveal distinct developmental behaviors reflecting their modes of fate determination.

The P1 blastomere shows autonomous specification. When isolated, it develops to produce all its usual descendant cell types, indicating that intrinsic factors within P1 dictate its developmental trajectory independent of external signals.

Conversely, the AB blastomere exhibits conditional specification. Isolated AB cells produce only a subset of their normal cell types, implying that interactions with other cells (such as P1 descendants) are required for the full expression of AB’s developmental potential.

This duality points to a combination of mechanisms shaping early development:

• Autonomous determination in P1 establishes a mosaic pattern with fixed cell fates.

• Conditional determination in AB allows regulative development, relying on cell-cell signaling.

Thus, the correct interpretation of the experimental results is:

(C) The determination of P1 was autonomous and AB was conditional.

(D) Both asymmetric division and cell-cell interactions specify cell fate in early development.

Hence, the appropriate choice is:

(4) C and D