The pair-rule gene fushi tarazu is expressed in the seven even-numbered parasegments during Drosophila embryogenesis. In contrast, the segment polarity gene engrailed is expressed in the anterior part of each of the 14 parasegments. Since both genes are active at similar times and places during development, it is possible that the expression of one gene is required for the expression of the other. This can be tested by examining expression of the genes in a mutant background—for example, looking at fushi tarazu expression in an engrailed mutant background, and vice versa. Given the hierarchy of gene action during Drosophila embryogenesis, what might you predict to be the result of these experiments?

Verified step by step guidance

1. Understand the hierarchy of gene action during Drosophila embryogenesis. Pair-rule genes like fushi tarazu are expressed earlier in development and help establish the segmented body plan, while segment polarity genes like engrailed refine and maintain the boundaries of these segments.
2. Consider the role of fushi tarazu in establishing the even-numbered parasegments. If engrailed expression depends on fushi tarazu, then a mutation in fushi tarazu might disrupt engrailed expression in the anterior part of the parasegments.
3. Analyze the role of engrailed in maintaining segment polarity. If fushi tarazu expression depends on engrailed, then a mutation in engrailed might disrupt the expression of fushi tarazu in the even-numbered parasegments.
4. Design the experiment to test these predictions. For example, examine fushi tarazu expression in an engrailed mutant background using techniques like in situ hybridization or immunostaining to visualize gene expression patterns.
5. Interpret the results based on the observed expression patterns. If fushi tarazu expression is unaffected in an engrailed mutant, it suggests that fushi tarazu acts upstream of engrailed. Conversely, if engrailed expression is disrupted in a fushi tarazu mutant, it supports the idea that engrailed depends on fushi tarazu for its expression.

Key Concepts

Pair-rule Genes

Pair-rule genes, such as fushi tarazu, are crucial in Drosophila embryogenesis as they define the segmentation of the embryo into alternating segments. They are expressed in a pattern that corresponds to every other segment, contributing to the establishment of the body plan. Their expression is essential for the proper formation of segments and influences the development of segment-specific structures.

Segment Polarity Genes

Segment polarity genes, like engrailed, are responsible for establishing the anterior-posterior polarity within each segment of the Drosophila embryo. They are expressed in specific regions of the segments and play a critical role in defining the boundaries and identity of segments. Their activity ensures that each segment develops distinct characteristics and maintains its integrity during development.

Gene Interaction and Mutant Analysis

The interaction between genes during development can be studied through mutant analysis, where the expression of one gene is examined in the absence of another. This approach helps to determine the dependency and regulatory relationships between genes. In the context of fushi tarazu and engrailed, analyzing their expression in mutant backgrounds can reveal whether one gene's expression is necessary for the other, providing insights into their functional hierarchy.