Vinegar fly

Vinegar fly ( Drosophila melanogaster ). Species of brachyceran dipteran of the family Drosophilidae.

It receives this name because it is found feeding on fruits in the process of fermentation such as apples , bananas, grapes , etc.

Summary

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• 1 Other names
• 2 Utility
• 3Desarrollo
  • 1 Stages of development
  • 2Desarrollo dorso-ventral
• 4 Structure of a segment
• 5Fuente

Other names

• Black-bellied dew lover, also called vinegarfly or fruit fly .

Utility

It is a species frequently used in genetic experimentation, given that it has a reduced number of chromosomes (4 pairs), short life cycle (15-21 days) and approximately 61% of known human disease genes have an identifiable counterpart. in the fruit fly genome , and 50% of fly protein sequences have analogs in mammals .

For research purposes, they can easily replace humans . They reproduce rapidly, so that many generations can be studied in a short space of time, and the complete map of their genome is already known. It was adopted as an animal for genetic experimentation by Thomas Hunt Morgan in the early 20th century . Its 165 Mb genome (1 Mb = 1 million base pairs) were published in March 2000 thanks to the public consortium and the company Celera Genomics. It houses around 13,600 genes .

Developing

From a cell derive daughter cells that generate a possible asymmetry. It presents an initial asymmetry in the distribution of its cytoplasmic components that gives rise to its differences in development. In oogenesis, follicular cells , nurse cells and the oocyte are generated. The fruit fly, at 29 ºC, can live 30 days; and from egg to adult 7 days. Early development determines the formation of axes.

The primordium develops differences in the axes: anteroposterior, dorsoventral. A succession of events derived from the initial asymmetry of the zygote results in the control of gene expression in such a way that different regions of the egg acquire different properties. This may occur due to the different localization of the transcription and translation factors in the egg or due to the differential control of the activities of these factors.

Then follows another stage in which the identities of the parts of the embryo are determined: regions are defined from which specific parts of the body derive. The genes that regulate the process encode transcription regulators and act on each other in a hierarchical manner and also act on other genes that are truly responsible for establishing this pattern (they act in a cascade).

Cell-cell interactions must also be taken into account as they define the boundaries between cell groups.

development stages

-The next stage of development depends on the genes that are expressed in the mother fly . These genes are expressed before fertilization. They can be divided into:

• Maternal somatic genes: expressed in somatic cells = follicular cells.
• Maternal germline genes: can act in both nurse cells and the oocyte.

There are four groups of genes involved in the development of the different parts of the embryo. Each group is organized in a different route that presents a specific order of action. Each pathway begins with events that take place outside the egg, resulting in the localization of a signal within the egg. These signals (proteins called morphogens) are distributed asymmetrically to fulfill different functions.

-Three systems are responsible for the antero-posterior axis and one is responsible for the dorso-ventral axis:

• Anterior System: responsible for the development of the head and chest. Maternal germline products are required to position the bicoid gene product at the front end of the egg.
• Posterior System: responsible for the segments of the abdomen. Many products are involved in localizing the nanos gene product, which inhibits hunchback expression in the abdomen.
• Terminal System: development of structures from the unsegmented ends of the egg. It depends on the maternal somatic genes (they activate the receptor encoded by torso).
• Dorso-ventral system: it is initiated by a signal from a follicular cell on the ventral side of the eggand is transmitted through the receptor encoded by the Toll gene. This results in the generation of a transcription factor activation gradient produced by the Dorsal gene.

All the components of the four systems are maternal, so the systems that establish the initial pattern depend on events prior to fertilization.

Dorso-ventral development

There is a complex interrelationship between the oocyte and follicular cells (genes from the oocyte are necessary for the development of follicular cells and their signals, transmitted to the oocyte, cause the development of ventral structures). Another pathway is responsible for dorsal development during egg growth. The systems function by activating a ligand-receptor interaction that triggers a transduction pathway.

The process depends, in its beginning, on the Gurken gene (which also acts in antero-posterior differentiation). Gurken mRNA is located on the posterior face of the oocyte causing adjacent follicular cells to differentiate into posterior cells . These cells send back a signal that triggers the production of a network of microtubules that is necessary for polarity.

Dorsoventral polarity is established when Gurken reaches the dorsal aspect of the oocyte (depends on the expression of several other genes).

Gurken’s product acts as a ligand by interacting with the receptor (Torpedo gene product) of a follicular cell .

The activation of this receptor triggers a signaling pathway whose final effect is to prevent the development of the ventral face in the dorsal (a change in the properties of the follicular cells of this face is produced). The development of ventral structures requires maternal genes that establish the dorso-ventral axis. The dorsal system is necessary for the development of ventral structures (such as mesoderm and neuroectoderm). Mutations in it prevent ventral development.

The ventral developmental pathway also begins in the follicular cells and ends in the oocyte. In the follicular cells, a series of signals are produced that end up generating a ligand for the receptor (product of the Toll gene, the first component of the pathway, which acts inside the oocyte).

Toll is the crucial gene in transporting the signal into the oocyte. The remaining components of the dorsal group encode products that either regulate or are necessary for Toll action. Toll is a transmembrane protein (homologous to the interleukin 1 receptor).

The binding of its ligand to the Toll receptor activates the pathway that determines ventral development. The distribution of the product of this gene is highly variable, but it only induces the formation of ventral structures in suitable places (it seems that active product is only expressed in certain regions).

Following ligand binding, the Toll receptor is activated on the ventral aspect of the embryo. This activation triggers a series of processes in which the products of other genes intervene and which ends in the phosphorylation of the product of the cactus gene, which is the final regulator of the transcription factor of the Dorsal gene.

In the cytoplasm there is an inactive cactus-dorsal complex but when phosphorylated cactus releases the dorsal protein, which enters the nucleus. Toll activation leads to dorsal activation.

A dorsal protein gradient is established in the nucleus from the dorsal to the ventral side of the embryo. On the ventral side, the dorsal protein is released into the nucleus but on the dorsal side, it remains in the cytoplasm .

The dorsal protein activates the Twist and Snail genes (necessary for the development of ventral structures) and inhibits the Decapentaplegic and Zerknullt genes (necessary for the development of dorsal structures). The initial interaction between gurken and torpedo leads to the repression of spatzle activity on the dorsal aspect of the embryo (toll ligand).

The dorsal protein, located in the nucleus, inhibits the expression of dpp. Thus, the ventral structures are formed according to a nuclear gradient of the dorsal protein and the dorsal structures according to a gradient of the dpp protein.

In the dorso-ventral axis there are three quite close bands that define the regions in which mesoderm, neuroectoderm and dorsal ectoderm are formed (ordered from ventral to dorsal).

Structure of a segment

-There are 3 groups of genes based on their effects on the structure of a segment:

• Maternal genes: expressed by the mother in oogenesis. They act during or after oocyte maturation. (an example is the bicoid gene).
• Segmentation genes: expressed after fertilization. They are responsible for the number and polarity of the segments (there are 3 groups that act sequentially to define the parts of the embryo).
• Homeotic genes: control the identity of the segments (not the number, polarity or size).