Ch. 18 - Developmental Genetics

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook

Sanders 3rd Edition

Ch. 18 - Developmental Genetics

Problem 18

Chapter 18, Problem 18

The bristles that develop from the epidermis in Drosophila are evenly spaced, so that two bristles never occur immediately adjacent to each other. How might this pattern be established during development?

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Step 1: Understand the concept of lateral inhibition. Lateral inhibition is a process where a cell, once it starts to differentiate into a particular type, sends inhibitory signals to its neighboring cells to prevent them from adopting the same fate.

Step 2: Consider the role of Notch signaling pathway. In Drosophila, the Notch signaling pathway is crucial for lateral inhibition. It helps in the communication between adjacent cells to ensure that they do not differentiate into the same type of cell, such as bristle cells.

Step 3: Explore the role of proneural clusters. During development, groups of cells called proneural clusters have the potential to become bristle cells. However, only one cell from each cluster will become a bristle cell, while the others will be inhibited.

Step 4: Analyze the selection of the sensory organ precursor (SOP) cell. Within each proneural cluster, one cell is selected to become the SOP cell, which will eventually develop into a bristle. This selection is influenced by the Notch signaling pathway, which ensures that only one cell in the cluster becomes the SOP.

Step 5: Examine the spatial patterning. The even spacing of bristles is a result of the lateral inhibition and the selection of SOP cells. As each SOP cell inhibits its neighbors, it ensures that no two bristles form adjacent to each other, leading to the characteristic pattern seen in Drosophila.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Pattern Formation

Pattern formation refers to the biological processes that lead to the spatial organization of cells and tissues during development. In Drosophila, this involves the regulation of gene expression and cell signaling pathways that dictate where and how structures like bristles will form. Understanding how these patterns emerge is crucial for explaining the even spacing of bristles.

Cell Communication

Cell communication is essential for coordinating developmental processes. In Drosophila, cells communicate through signaling molecules that influence neighboring cells' behavior, ensuring that bristles are spaced apart. This communication can involve mechanisms such as lateral inhibition, where a cell inhibits its neighbors from adopting the same fate, thus preventing adjacent bristles.

Genetic Regulation

Genetic regulation involves the control of gene expression that determines the characteristics of an organism. In the context of Drosophila bristle development, specific genes are activated or repressed to establish the pattern of bristle formation. Understanding the genetic pathways and regulatory networks that govern this process is key to explaining how the even spacing of bristles is achieved.

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Regulation

Related Practice

Textbook Question

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?

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Textbook Question

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 the expression of the genes in a mutant background—for example, looking at fushi tarazu expression in an engrailed mutant background, and vice versa. Based on your prediction, can you predict the phenotype of the fushi tarazu and engrailed double mutant?

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Textbook Question

In contrast to Drosophila, some insects (e.g., centipedes) have legs on almost every segment posterior to the head. Based on your knowledge of Drosophila, propose a genetic explanation for this phenotype, and describe the expected expression patterns of genes of the Antennapedia and bithorax complexes.

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Textbook Question

You are traveling in the Netherlands and overhear a tulip breeder describe a puzzling event. Tulips normally have two outer whorls of brightly colored petal-like organs, a third whorl of stamens, and an inner (fourth) whorl of carpels. However, the breeder found a recessive mutant in his field in which the outer two whorls were green and sepal-like, whereas the third and fourth whorls both contained carpels. What can you speculate about the nature of the gene that was mutated?

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Textbook Question

A powerful approach to identifying genes of a developmental pathway is to screen for mutations that suppress or enhance the phenotype of interest. This approach was undertaken to elucidate the genetic pathway controlling C. elegans vulval development. A lin-3 loss-of-function mutant with a vulva-less phenotype was mutagenized. Based on your knowledge of the genetic pathway, what types of mutations will suppress the vulva-less phenotype?

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Textbook Question

A powerful approach to identifying genes of a developmental pathway is to screen for mutations that suppress or enhance the phenotype of interest. This approach was undertaken to elucidate the genetic pathway controlling C. elegans vulval development. In a complementary experiment, a gain-of-function let-23 mutant with a multi-vulva phenotype was also mutagenized. What types of mutations will suppress the multi-vulva phenotype?

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