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Its development starts in the space found within Germanium, where one of the progenitors of oocyte, called stem cell undergoes mitotic cell division to give 16 cells, where each of the cells are connected by one or two cytoplasmic bridges.
Earlier embryologists used histochemical methods to study development of organisms; which has provided anatomical details of development.This is not true for all multicellular organisms.(2008)suggests that more recently, it is used mostly in developmental biology, looking to see how a complex organism arises from a relatively simple fertilised egg.Embryonic development is where most of the attention is concentrated, but there is also a great deal of interest in how various adult structures develop in the pupa, mostly focused on the development of the compound eye, but also on the wings, legs and other organs.Molecular basis of this differentiation and development is profound.Initial stages of such events have been very well elucidated in Drosophila.The Illustration of the germarium; shows the stem cells (yellow), which divide to produce a daughter cystoblast (blue).
The daughter cells divide incompletely to produce a cyst of 16 cells (blue) joined by actin-rich ring canals (red), with a continuous fusome (grey).
As the cyst matures it moves along the germarium and is surrounded by somatic follicle cells (green), which intercalate and pinch it off to form a discrete egg chamber.
Columnar follicle cells (C), illustrating their polarized membrane domains, apical (orange), adherens junction (dark green) and basolateral (yellow), and cytoskeleton, with Actin (red) and microtubules (grey).
Whether an organism is unicellular or multicellular, cells go through a series of gene expressions to reach a particular stage of development; the reproduction and growth of an organism is all due to molecular expression in stepwise manner, from a young cell to an adult cell ready for reproduction.
During development, a single precursor cell with repeated cell divisions generates a series of progenitors, which in turn undergo programmed differentiation into specific fate.
The thorax is made up of Prothorax (with first pair of legs and pair of humeri); a Mesothorax with a pair of wings and a pair of legs.