The Question is from neet-botany plant-growth-and-development , and it was created by the author B VENKAT

Question

During human embryonic development, the formation of the primitive streak marks a crucial step. Which of the following statements regarding the primitive streak is INCORRECT?

B VENKAT · Accepted Answer

## CORE INFORMATION
✓ **Answer**: D
## CONCEPT FRAMEWORK
	**Primary Concept**: Gastrulation and Embryonic Development
	**Related Topics**: Embryonic axes, Germ layers, Neurulation
	**Prerequisites**: Basic understanding of human development stages
## SOLUTION PATHWAY
**Given Information**:
	The question asks about the incorrect statement regarding the primitive streak.
**Method & Steps**:
	1. Analyze each option based on its accuracy about the primitive streak's role.
	2. Identify the statement that deviates from established embryological principles.
	3. Confirm the correct statements to highlight the incorrect one by contrast.
## OPTION ANALYSIS
[A] ✓: It marks the beginning of gastrulation.  The primitive streak is the defining feature initiating gastrulation, where the bilaminar disc transforms into a trilaminar disc (ectoderm, mesoderm, and endoderm).
[B] ✓: It defines the embryo's axes.  The primitive streak establishes the anterior-posterior (head-tail), and medial-lateral (midline-sides) axes of the developing embryo. The node at the anterior end of the streak is crucial for defining the left-right axis.
[C] ✓: It is the source of mesoderm and endoderm.  Cells migrate through the primitive streak to form the mesoderm and endoderm. The cells remaining on the surface form the ectoderm.
[D] :x: It persists throughout development. This is the incorrect statement. The primitive streak regresses and disappears by the end of the fourth week of development.  Remnants of the primitive streak can lead to tumors (e.g., sacrococcygeal teratomas).
## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing the roles of the primitive streak and the notochord: The notochord defines the midline and is crucial for inducing the neural tube, while the primitive streak initiates gastrulation and defines the initial axes.
		2. Assuming persistence of embryonic structures: Many transient embryonic structures, like the primitive streak, appear and disappear during development.  Their presence at later stages can indicate developmental abnormalities.
	**Quick Tips**:
		1. Remember 'streak' as the 'starting line' for gastrulation.
		2. Visualize the primitive streak as a temporary structure essential for the early organization of the embryo.

B VENKAT · Answer

It marks the beginning of gastrulation.

B VENKAT · Answer

It defines the embryo's axes.

B VENKAT · Answer

It is the source of mesoderm and endoderm.

B VENKAT · Answer

The correct Option is "It persists throughout development."

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