Posterior Dominance in the context of somites refers to the tendency for the more posterior (tailward) somites to influence the development of anterior (headward) somites during embryogenesis. This phenomenon plays a crucial role in establishing the body plan of vertebrates.

What are the main features of posterior dominance?

• Somite Progression: Somites are blocks of mesoderm that form sequentially from head to tail along the embryonic axis.
• Influencing Development: Posterior somites can influence the fate and differentiation of anterior somites, leading to the formation of distinct structures in different body regions.
• Gradients: This influence often involves the establishment of gradients of signaling molecules that are produced by posterior somites and act on anterior somites.

What is the importance of posterior dominance?

• Body Plan Establishment: Posterior dominance is essential for establishing the proper body plan, ensuring that different body segments develop in the correct order and with the appropriate structures.
• Regionalization: By influencing the development of anterior somites, posterior somites contribute to the regionalization of the body, leading to the formation of distinct structures in different regions, such as the head, trunk, and tail.
• Evolutionary Significance: Understanding posterior dominance can provide insights into the evolutionary mechanisms that have shaped the diversity of body plans among different species.

What are the applications of posterior dominance in practice?

• Developmental Biology: Studying posterior dominance can help researchers understand the molecular mechanisms that regulate embryonic development and the formation of different body structures.
• Evolutionary Biology: Comparing posterior dominance patterns in different species can provide insights into the evolutionary history of vertebrates and the mechanisms that have led to the diversity of body plans.
• Medical Research: Understanding the role of posterior dominance in development may be relevant for studying birth defects and other developmental disorders.

Example

A well-known example of posterior dominance is the influence of posterior somites on the development of the spinal cord. The neural tube, which will become the spinal cord, forms in response to signals from the underlying somites. Posterior somites can influence the differentiation of neural tube cells, leading to the formation of different types of neurons and the establishment of the spinal cord's regional organization.

Critical comments

While posterior dominance is a well-established phenomenon, the precise molecular mechanisms underlying this process are still being investigated. Further research is needed to fully understand the role of signaling molecules, gene expression, and other factors in mediating the influence of posterior somites on anterior development. Additionally, the evolutionary significance of posterior dominance and its role in the diversification of body plans among vertebrates remains an active area of research.