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Segmentation in biology is the division of some animal and plant body plans into a linear series of repetitive segments that may or may not be interconnected to each other. This article focuses on the segmentation of animal body plans, specifically using the examples of the taxa Arthropoda , Chordata , and Annelida .
Segmentation is the physical characteristic by which the human body is divided into repeating subunits called segments arranged along a longitudinal axis. In humans, the segmentation characteristic observed in the nervous system is of biological and evolutionary significance. [1]
A segmentation gene is a gene involved in the early developmental stages of pattern formation. It regulates how cells are organized and defines repeated units in the embryo. Segmentation genes have been documented in three taxa: arthropods (i.e. insects and crabs), [2] chordates (i.e. mammals and fish), and annelids (i.e. leeches and earthworms).
Earthworms are a classic example of biological homonymous metamery – the property of repeating body segments with distinct regions. In biology, metamerism is the phenomenon of having a linear series of body segments fundamentally similar in structure, though not all such structures are entirely alike in any single life form because some of them perform special functions. [1]
Segmentation (biology) – Division of some animal and plant body plans into a series of segments; Supernumerary body part – Growth of an additional part of the body and a deviation from the body plan; Symmetry in biology – Geometric symmetry in living beings
The gap genes code for transcription factors that regulate the expression of pair-rule genes and homeotic genes [8] by competing for binding to their enhancer regions. It has been demonstrated that gap gene expression in the Drosophila blastoderm exhibit a property called canalization, a property of developing organisms to produce a consistent phenotype despite variations in genotype or ...
The gooseberry gene's role in segmentation was believed to be involved in segment-polarity class of segmentation genes required for the formation of larval segments because, during embryogenesis, half of the larval segments are replaced by the remain half segment, but in a reversed polarity, which suggested that gooseberry was a single gene. [8]
The number of somites is species dependent and independent of embryo size (for example, if modified via surgery or genetic engineering). Chicken embryos have 50 somites; mice have 65, while snakes have 500. [4] [8]