Consider the even-skipped regulatory sequences in Figure 18.9.

Explain what you expect to see happen to even-skipped stripe 2 if it is expressed in a Krüppel mutant background. What about a hunchback mutant background? A giant mutant background? A bicoid mutant background?

Key Concepts

Even-skipped Gene Function

The even-skipped (eve) gene is a key regulator in the segmentation of Drosophila embryos, responsible for establishing specific stripe patterns during development. It is expressed in a series of stripes, with each stripe corresponding to a segment of the embryo. The regulation of eve expression is influenced by various transcription factors, which can either activate or repress its expression in specific regions.

Mutant Backgrounds and Their Effects

Mutant backgrounds, such as Krüppel, hunchback, giant, and bicoid, refer to genetic alterations that affect the normal expression of genes involved in developmental processes. Each of these mutations disrupts the gradients of transcription factors that regulate the expression of the eve gene, leading to altered stripe patterns. Understanding how these mutations impact eve expression is crucial for predicting developmental outcomes.

Transcription Factor Interactions

Transcription factors are proteins that bind to specific DNA sequences to regulate gene expression. In the context of the even-skipped gene, factors like Krüppel, hunchback, giant, and bicoid play significant roles in determining where and when eve is expressed. The interactions between these factors can lead to either enhancement or suppression of eve expression, which is essential for proper segmentation in the embryo.