Drosophila melanogaster

Physical aspect

These flies are of yellowish color brown, with black transverse rings through the abdomen. They have red eyes. They present a sexual Dimorphisme: the females measure approximately 2,5 millimetres length; the males are a little smaller and the back part of their body is darker. For a neophyte who would try to describe the difference between the sexes under a microscope, the distinctive character most outstanding is probably the cluster of poils enourant the anus and the genitals of the male. On the Web site Flybase on this subject (see lower bond), one finds images concrete.

Life cycle

The life cycle of Drosophila melanogaster lasts approximately two weeks with 25 °C; the cycle takes twice more time with 18 °C. The females lay approximately 400 eggs (embryos) in fruits in putrefaction or other organic materials. The eggs have a length of approximately 0,5 millimetres. The Larve leaves egg after 24:00 and grows during five days in moulting twice, 24 and 48 H after the blossoming. During their growth, they nourish micro-organisms which break up the fruit, as well as sugars of the fruit itself. Then, the larvae encapsulate themselves in the Pupa rium and undergo a metamorphosis which lasts five days, following which the adult emerges.

The females couple themselves approximately 12 hours after being left their pupe. They store the Sperme males to which they were coupled to be able to use it later on. For this reason, the geneticists must capture the female flies before their first sexual relation, i.e. a virgin female, and make sure that they are coupled only with the precise male required by the experiment. According to the " red book" (red book) of Michael Ashburner, the inséminées females can be " Re-virginisées" by prolonged incubation with -10 °C, which kills sperm.

An exceptional guinea-pig in genetics

Drosophila melanogaster is one of the model organizations studied in biological research, in particular in genetics and biology of the development. There are several reasons for that:

They are small and easy to raise in laboratory
Their cycle of generation is short (approximately 2 weeks) and has a great productivity (the females can lay to 500 eggs in 10 days)
the mature larvae have giant chromosomes in salivary glands.
They have only 4 pairs of Chromosome S: 3 autosomiques, and 1 sexual.
the males do not carry out a recombination, which facilitates the genetic studies.
Of the techniques of genetic transformation is available since 1987.
Them Génome, which is compact, was sequence in 1998.

Thomas Hunt Morgan accomplish his studies one heredity. " Thomas Hunt Morgan and colleagues extended Mendel 'S work by describing X-linked inheritance and by showing that constrained located one the same chromosome C not show independent assortment. Milked studies off X-linked helped confirm that constrained are found one chromosomes, while milked studies off linked led to the first maps showing the hirings off genetic loci one chromosomes" (Freman 214). The first maps off Drosophila chromosomes were completed by Alfred Sturtevant. -->

The genome of the Drosophila

The Génome of the Drosophila contains 4 pairs of chromosomes: a pair X/Y, and three autosomes called 2,3, and 4. The fourth chromosome is so tiny that it is often omitted. The genome contains approximately 165 million bases and approximately 13 000 genes. The genome finished being sequence in 2000 and put in chart.

Similarity compared to the human ones

From a genetic point of view, the human beings and the drosophilas are similar. Approximately 61% of genes of known diseases have a recognizable correspondence with the genetic code of the drosophilas, and 50% of proteins of this fly have analogues in the mammals. Drosophila is used as genetic model for various human diseases of which the Parkinson's disease and that of Huntington.

Determinism of the sex in the drosophila

The Y chromosome does not define the male sex in the fly as at the human being. It is the relationship between the number of autosomaux genes determining the male character and the number of genes females related to the X chromosomes which imports. Thus a fly XY can phénotypiquement be a female if the balance between the number of determining genes male and female leans in favor of the determinism female.

Genetic nomenclature

The name of genes named according to alleles Récessif S starts with tiny, that of the dominant alleles by a capital letter. The genes which owe their name with a protein derivative start with tiny. The genes are typically written in italics. The convention of writing of the genotypes is:

X/Y; 2nd/2nd; 3rd/3rd . ²

In the community of the Molecular biology, the genticians, working on Drosophila are known for their system of somewhat whimsical naming of the changes discovered. Compared with the more strict names (but also more practical: " example; cdc4" , " cdk4" , etc) in the geneticists of the yeast Saccharomyces cerevisiae, the drosophilists give favor to names such as " cheap date" (" poor appointment ") (a change leading to a sensitivity increased to the intoxication to the ethanol or " snafu" (a change leading to grotesque anatomical anomalies).

Development and embryogenesis

See the principal article: Embryogenesis of Drosophila Embryogenesis in Drosophila has been extensively studied, the small size, wide shorts time generation, and brood size makes it ideal for genetic studies. Single It is also among model organisms in that cleavage occurs in has Syncytium. --> Butt 5000 nuclei accumulate in the unseparated cytoplasm off the oocyte before they migrate to the surface and are encompassed by plasma membranes to form concealments surrounding the yolk bag. Early one, the germ line segregates from the somatic concealments through the formation off pole concealments At the posterior end off the embryo.

Concealment division in the early Drosophila embryo happens so quickly there are No proper checkpoints so mistakes may Be made in division off the DNA. To get around this problem the nuclei which cuts made has mistake detatch from to their Centrosome S and fall into the center off the embryo which will not form share off the fly. -->

Genetics of the behavior and neuroscience

Since then Benzer, his students and many other cuts used behavioral screens to isolate constrained involved in vision, smell, hearing, learning/memory, courtship, bread and other processes such ace longevity. -->

Vision at the Drosophila

A eye made up of drosophila contains 800 units of vision or Ommatidia, which does of it one the most developed of among the insects. Each ommatidium contains 8 cells photoréceptrices (R1-8), of the cells of support, the cells of pigment, and a cornea. The drosophilas standard cells of reddish pigment have, which are used to absorb the excess of blue light what prevents the dazzling of the fly by the ambient light.

nucleus while the rhabdomere is made up off toothbrush-like stacks off membrane called Microvilli. Each microvillus is 1 mm to 1.5 mm in length and 50 Nm in diameter. The membrane off the rhabdomere is packed with butt 100 million Rhodopsin molecules, the visual protein that absorbs light. The rest off the visual proteins are also tightly packed into the microvillar space, leaving little room for Cytoplasm.

The photoreceptors in Drosophila express train has variety off Rhodopsin isoforms. The R1-R6 photoreceptor concealments express train Rhodopsin1 (Rh1) which absorbs blue light (480 Nm). The R7 and R8 concealments express train has combination off either Rh3 gold Rh4 which absorb UV light (345 Nm and 375 Nm), and Rh5 gold Rh6 which absorb blue (437 Nm) and green (508 Nm) light respectively. Each Rhodopsin molecule consists off year opsin protein covalently linked to has Carotenoid chromophoric, 11-cis-3-hydroxyretinal.³

Ace in vertebrate vision, visual transduction in Invertebrate S occurs via has G protein-coupled pathway. However, in Vertebrates the G protein is transducin, while the G protein in invertebrates is Gq (dgq in Drosophila ). When Rhodopsin (Rh) absorbs has chromophoric Photon off light its, 11-cis-3-hydroxyretinal, is isomerized to al3. Rh undergoes has conformational changes into its activates form, metarhodopsin. Metarhodopsin activates Gq, which in turn activates has Phospholipase Cβ (PLCβ) known ace NorpA. --> 2), has Phospholipid found in the Cell membrane, into soluble Inositol triphosphate (IP₃) and Diacylgycerol (DAG), which stays in the Cell membrane. DAG gold has derivative DAG causes off has Calcium selective Ion Chanel known ace TRP (transient receptor potential) to open and Calcium and Sodium flows into the concealment. IP₃ is thought to bind to IP₃ receptors in the Subrhabdomeric cisternae, year extension off the Endoplasmic reticulum, and causes release off Calcium, goal this process doesn' T seem to normal Be essential for vision.⁴

Calcium binds to proteins such ace Calmodulin (Camwood) and year eye-specific protein kinase C (PKC) known ace InaC. Thesis proteins interact with other proteins and cuts been shown to Be necessary for shut off off the light response. In addition, proteins called Arrestin S bind metarhodopsin and prevent it from activating more Gq.

With Potassium - depend Sodium/calcium exchanger known ace NCKX30C pumps the Calcium out off the concealment. It use the inward sodium gradient and the outward potassium gradient to extrudes calcium At has Stoichiometry 4 off Na⁺/1 Ca⁺⁺, 1 K⁺.⁵

TRP, InaC, and PLC form has signaling complex by binding has scaffolding protein called InaD. Five InaD contains binding domains called PDZ domains which specifically bind the C termini off target proteins. Disruption off the complex by changes in either the PDZ domains gold the target proteins reduces the efficiency off signaling. For example, disruption off the interaction between InaC, the protein kinase C, and InaD results in has delay in inactivation off the Light response.

Unlike Vertebrate metarhodopsin, Invertebrate metarhodopsin edge Be converted back into Rhodopsin by absorbing has Photon off orange light (580 Nm).

Approximately two-thirds off the Drosophila brain (butt 200,000 will neurons total) is dedicated to visual processing. Space Although the resolution off to their vision is significantly worse than that off humans, to their temporal resolution is approximately ten times better. -->

Flight of the Drosophila

The wings of a fly can beat up to 250 times a second. The flies fly by direct sequences of movement alternating with rapids rotations called Saccade S. During these rotations, a fly can carry out a rotation of 90 degrees in less than 50 milliseconds.

Long It was thought that the characteristics off Drosophila flight were dominated by the Viscosity off the air, rather than the Inertia off the fly body. However, recent research by Michael Dickinson and Rosalyn Sayaman has indicated that flies perform banked turns, where the fly accelerates, slow fox trots down while turning, and accelerates again At the end off the turn. This indicates that inertia is the dominating force, ace is the box with larger flying animals. -->

External bonds (in English)

has quick and simple introduction to '' Drosophila melanogaster ''
FlyBase
The WWW Virtual Library: Interactive Drosophila
The Berkeley Drosophila Genome Project
Keeping and Breeding Fruit Flies
Abstract off the papers describing the genome off Drosophila melanogaster
FlyMove
The Fly - has guide to Drosophila constrained and to their development roles in
Drosophila Nomenclature - naming off constrained

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