Question

Which one function as primary organiser in frog?

• A. Dorsal tip of gastrula
• B. Grey crescent
• C. Chordamesoderm of gastrula
• D. Any of the above

Answer 1

Answer: (B)

Grey crescent

The gray crescent establishes the bilateral symmetry of the frog. Even before the first cleavage event, we can tell how the frog will develop. The first cleavage plane always bisects the gray crescent. The site of sperm entry will become the ventral region of the frog (the belly). The gray crescent will become the dorsal region of the frog. Hence the Grey crescent acts as the primary organiser in a frog.

So the correct answer is 'Grey crescent'.