Axes and pattern formation in drosophila.pptx

Axes and pattern formation in drosophila - Dr.M.Jothimuniyandi

1. Axes and pattern formation in drosophila Dr.M.Jothimuniyandi Assistant Professor

2. Axes and pattern formation in drosophila Axes and pattern formation in Drosophila melanogaster (fruit fly) is a well-studied example in developmental biology. It involves the establishment of the body plan along the anterior-posterior (head-to-tail) and dorsal-ventral (back-to-belly) axes.

3. Anterior-Posterior Axis Formation Maternal Effect Genes: The mother deposits mRNAs into the egg, which determine the anterior-posterior polarity. The most critical of these genes are bicoid and nanos . Bicoid : Concentrates at the anterior end of the embryo and acts as a morphogen , forming a gradient that instructs the cells in the anterior region to develop head and thorax structures. Nanos: Localized at the posterior end, responsible for repressing anterior genes and promoting posterior development.

4. Anterior-Posterior Axis Formation Gap Genes: These are zygotic genes that divide the embryo into broad regions. Examples include hunchback and knirps . Pair-Rule Genes: These genes further segment the embryo into alternating stripes. Even-skipped and fushi tarazu are key examples.

5. Anterior-Posterior Axis Formation Segment Polarity Genes: These refine the boundaries between segments, determining the anterior and posterior parts of each segment. Engrailed and wingless are important here . Homeotic ( Hox ) Genes: These genes specify the identity of individual segments, ensuring that each one forms the appropriate structures.

6. Dorsal-Ventral Axis Formation Dorsal Protein: The localization of the dorsal protein helps establish dorsal-ventral polarity. Dorsal enters the nuclei of cells on the ventral side of the embryo, where it activates genes that determine ventral fates. Decapentaplegic ( dpp ): On the dorsal side, the dpp gene is active, promoting dorsal development. Dpp is opposed by short gastrulation in ventral regions.

7. Pattern Formation These gradients and gene interactions create a positional information map for the developing embryo. Cells interpret their position in the embryo based on the concentration of these morphogens, which leads to the establishment of specific tissues and organs.

8. Pattern Formation The early embryo is patterned through a cascade of gene regulation that begins with maternal effect genes and leads to a progressively more refined segmentation. Each stage of this process provides positional information, ensuring that the embryo's body plan develops with the appropriate structures in the correct locations.

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