Animal Developmental Patterns · Zoology

In amphibian development, what is the primary role of the 'Gray Crescent' formed after fertilization?

  1. It marks the future site of the mouth
  2. It serves as the site where gastrulation begins
  3. It is the region where the yolk is most concentrated
  4. It triggers the formation of the extraembryonic membranes
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Correct answer: It serves as the site where gastrulation begins

The Gray Crescent forms opposite the point of sperm entry due to cortical rotation. This region contains cytoplasmic determinants that define the dorsal-ventral axis and initiate the formation of the blastopore lip.

Difficulty: Medium Question 2 of 20

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