Fly development illustrates three important principles in de

Fly development illustrates three important principles in development: (a) the use of \"morphogenetic gradients\", (b) hierarchical \"genetic cascades\", and (c) the \"progressive specification\" of body parts. Describe what is meant by each of these three terms.

Solution

Fly development illustrates three important principles in devlopment. They are

a) The use of morphogenetic gradients.

b) Hierarchical genetic cascades

Progressive specification of body parts.

a) The use of morphogenetic gradients:

Morphogenes are signalling molecules. Morphogenetic gradients play a important role in organ patterning and organ growth.They are several models present in growth control by morphogenetic gradients.For example in mechanical stress model, the proliferation of cells were occur in central region in response to morphogen and stretches to periphery causing them to divide.The fate of each cell depends on the level of morphogen signal and concentration gradient.

b) Hierarchial genetic cascades:

Gene cascades are chain reactions involved in gene expression. The transcription factor genes have the code that produces proteins that activates or repress the expression of other genes. In a cell, as one gene activates, it produces, along with the proteins it must produce for its function , chemicals which activate other genes within itself or other cells.This is important for limb formation in flies.

c) Progressive specification of body parts:

In flies, nervous system develops a progressive process of cell fate specification. Expression of specific proneural genes in clusters of cells in the cellular blastoderm give these cells with the potential to form certain types of neural precursors. The development of body parts like wings develop progressively based on interaction between the cytoplasmic material in the neural systems.