DB Chapter 11: Early development in drosophila melanogaster at Hochschule Bonn-Rhein-Sieg

Embryos are relatively complex, small and intransparent

Chorion is a shell than surrounds the egg. Micropyle is the small opening of it, that allows passage of one sperm at a time.

extremely long, about 1,8 mm. It prevents other sperms from passing through the micropyle (polyspermy block). 

before the sperm enters.

Meroblastic superficial cleavage.

The expression of zygotic genes begins around cycle 11 and is greatly enhanced when cells are formed at cycle 14. 

Because of the appearance of gap phases in the cell cycle. 

Maternal RNA is degraded and the zygotic genome takes over control of development. 

By the ratio of chromatin to cytoplasm

Soon after mid-blastula transition.

Terminal portion of the head

Tail