Early development in Drosophila is atypical in that pattern formation takes place in a syncytial blastoderm, allowing free diffusion of transcription factors between nuclei. In many other animal species, the fertilized egg is divided by cellular cleavages into a larger and larger number of smaller and smaller cells.

How must the model that describes Drosophila development be modified for describing animal species whose early development is not syncytial?

Key Concepts

Syncytial Blastoderm

A syncytial blastoderm is a stage in early embryonic development where multiple nuclei share a common cytoplasm without cellular boundaries. In Drosophila, this allows for the free diffusion of transcription factors, facilitating coordinated gene expression across the embryo. Understanding this concept is crucial for comparing it to other developmental models where individual cells are formed early on.

Cellular Cleavage

Cellular cleavage refers to the series of rapid mitotic divisions that occur after fertilization, resulting in the formation of smaller cells called blastomeres. In many animal species, this process leads to a multicellular embryo, where each cell can develop independently. Recognizing how cleavage patterns differ from syncytial development is essential for modifying models of embryogenesis.

Transcription Factors

Transcription factors are proteins that regulate gene expression by binding to specific DNA sequences. In the context of early development, they play a critical role in determining cell fate and organizing the body plan. In a syncytial environment, transcription factors can diffuse freely, whereas in a cellular environment, their distribution and activity must be tightly regulated within individual cells.