Absence of rhizoids is the characteristic feature of
**Core Concept**
The question is testing the student's knowledge of embryological development, specifically the formation of the neural tube during embryogenesis. Rhizoids are small, root-like structures that are involved in the formation of the neural tube. Their absence is a key feature of a specific neural tube defect.
**Why the Correct Answer is Right**
The correct answer is related to the neural tube defect where the closure of the neural tube is incomplete, resulting in the absence of rhizoids. During embryogenesis, the neural plate folds in on itself to form the neural tube. In the case of spina bifida, the neural tube fails to close properly, leading to the absence of rhizoids. This is due to a failure of the neural plate to undergo proper folding and closure, resulting in an open neural tube.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not relate to the absence of rhizoids. Rhizoids are specific to the neural tube, and their absence is a characteristic feature of spina bifida.
* **Option B:** This option is incorrect because it is unrelated to the neural tube and rhizoids. Anencephaly is a different neural tube defect where the cranial end of the neural tube fails to close.
* **Option C:** This option is incorrect because it is not directly related to the absence of rhizoids. Meningocele is a type of spina bifida where the meninges protrude through a defect in the vertebrae, but it is not characterized by the absence of rhizoids.
**Clinical Pearl / High-Yield Fact**
Rhizoids are small, root-like structures that are involved in the formation of the neural tube. Their absence is a key feature of spina bifida, a neural tube defect where the neural tube fails to close properly.
**Correct Answer:** D.