In this chapter, we have focused on large-scale as well as the inter- and intracellular events that take place during embryogenesis and the formation of adult structures. In particular, we discussed how the adult body plan is laid down by a cascade of gene expression, and the role of cell–cell communication in development. Based on your knowledge of these topics, answer several fundamental questions:

How do we know that molecular gradients in the egg of Drosophila exist?

Key Concepts

Molecular Gradients

Molecular gradients refer to the uneven distribution of molecules, such as proteins or mRNA, within a cell or tissue. In the context of Drosophila embryogenesis, these gradients are crucial for establishing polarity and guiding the development of body structures. They influence gene expression patterns and cell fate decisions during early development.

Gene Expression Cascade

A gene expression cascade is a series of regulatory events where the expression of one gene triggers the expression of another, leading to a coordinated response in development. In Drosophila, this cascade is essential for the proper formation of the body plan, as it dictates the timing and location of specific developmental genes being activated in response to molecular gradients.

Cell–Cell Communication

Cell–cell communication involves signaling mechanisms that allow cells to interact and coordinate their activities during development. In Drosophila, this communication is vital for interpreting molecular gradients and ensuring that cells respond appropriately to their environment, which is essential for the correct formation of tissues and organs during embryogenesis.