What causes a gray crescent to appear in many frog embryos?
Selected answer will be automatically saved. For keyboard navigation, press up/down arrow keys to select an answer.
a
The gray crescent appears as an indentation representing the start of the first cleavage.
b
The outer (cortical) cytoplasm rotates relative to the internal cytoplasm.
c
A thickening of the cytoplasm occurs at the site of sperm entry.
d
The sperm centrioles are gray and provide color to the cytoplasm.
a
The gray crescent appears as an indentation representing the start of the first cleavage.