Consider the even-skipped regulatory sequences in Figure 18.9.

How are the sharp boundaries of expression of eve stripe 2 formed?

Key Concepts

Regulatory Sequences

Regulatory sequences are regions of DNA that control the expression of genes. They can include enhancers, silencers, and promoters, which interact with transcription factors to regulate when and where genes are turned on or off. In the context of the even-skipped (eve) gene, these sequences play a crucial role in establishing the precise patterns of gene expression necessary for proper development.

Transcription Factors

Transcription factors are proteins that bind to specific DNA sequences to regulate gene expression. They can act as activators or repressors, influencing the transcription of target genes. In the case of eve stripe 2, specific transcription factors bind to the regulatory sequences, creating sharp boundaries of expression by promoting transcription in certain regions while inhibiting it in others.

Positional Information and Morphogens

Positional information refers to the spatial cues that cells use to determine their location and fate during development. Morphogens are signaling molecules that provide this information, often creating concentration gradients that influence gene expression. In the formation of eve stripe 2, morphogen gradients help establish the boundaries of expression by providing cells with information about their position relative to the source of the morphogen.