Which statement about frog eggs is true?
A) Sperm-binding sites occur uniformly over the surface of the egg.
B) Microtubules organized by the sperm's centriole guide movements of cortical cytoplasm.
C) The gray crescent is a band of the most darkly pigmented cytoplasm in a fertilized frog egg.
D) Inner cytoplasm rotates, relative to cortical cytoplasm, toward the site of sperm entry.
E) The gray crescent marks the location of sperm entry.

Question

Quizplus · Accepted Answer

Microtubules organized by the sperm's centriole guide movements of cortical cytoplasm during fertilization in frogs. This helps to determine the dorsal-ventral and anterior-posterior axes of the developing embryo.

Answer: C
 The gray crescent is a band of the most darkly pigmented cytoplasm that appears on one side of a frog egg after fertilization. It marks the future dorsal side of the embryo and is important in establishing its symmetry.

Answer: D
 The inner cytoplasm of a fertilized frog egg rotates, relative to cortical cytoplasm, toward the site of sperm entry. This movement is driven by microtubules and helps distribute cytoplasmic determinants throughout the zygote.

Option A is false. Sperm-binding sites are concentrated at the animal pole of frog eggs.
Option E is also false. The gray crescent does not mark the location of sperm entry, but rather marks the future dorsal side of the embryo.

Which Statement About Frog Eggs Is True