Correct option is D
Explanation of Option 4:
"It develops into ectoderm."
This is the correct answer because the grafted vegetal pole blastomere, when placed at the animal pole, will assume the fate of the surrounding environment, which is ectodermal. This phenomenon is due to conditional specification, where the fate of a cell is influenced by its location and the signals it receives from surrounding cells.
The grafted cell will undergo reprogramming and will not follow its default fate (endoderm), but instead will take on the ectodermal fate that is typical for animal pole cells. This is a well-documented concept in developmental biology where cells adopt the fate dictated by the surrounding tissues' signaling.
Incorrect Options:
It organizes the surrounding tissue to generate a secondary body axis.
While this could happen in some induction scenarios, it’s not the most accurate description of the outcome in this case. The vegetal blastomere will develop into ectoderm in this case, not induce a full secondary body axis. This specific case is more about fate specification influenced by position, rather than full axis formation.
It completely disrupts development.
This is unlikely. The embryo still follows conditional specification principles, and even though the grafted vegetal cell takes on the ectodermal fate, it will not disrupt development completely. Instead, it will adopt a new fate. This is not a disruption.
It develops into endoderm.
The vegetal blastomere is normally fated to become endoderm, but when grafted to the animal pole, it will take on the ectodermal fate due to the signaling from surrounding animal pole cells. Thus, it will not develop into endoderm in this case. The new position overrides the default developmental fate.
