2009 Group Project 2

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FLY

Drosophila Melanogaster

Drosophila melanogaster, the common fruit fly plays a major role in embryological and genetic research. Due to their size and their ability to be easily reared in small spaces, they have a short lifespan so that new generations can be studied within a few weeks and females can lay up to 100 eggs per day. They are cost effective for schools and universities, allowing easy replication of studies for on going years and large populations mean statistical analysis can be easy to obtain and is reliable. The complete genome was sequenced and published in 2000.

The object of this page is to examine the embryological development of Drosophila. However, the embryological development of Drosophila is just the beginning, as this development occurs within the female parent fly before birthing. Post-natal development has two separate periods in which the embryo develops to become a fully grown adult fly. These periods are the larval stage, and the pupal stage. In these stages the embryo goes through a metamorphosis changing its external appearance, and growing appendages such as wings, legs, and antennae, becoming a fully functional adult fly.

Timeline of Drosophila Development

Stages of Drosophila Development

The stages listed below are adapted from Bownes stages (1975) by Ortega and Hartenstein (1985), as there were some dissimilarities and inconsistencies observed in Bownes stages. The following times given for the stages are an average recorded room temperature (25°C).

Table 1: Stages of Drosophila development
Stage Time since fertilisation (hours) Stage Characteristic embryo characteristic
1 0.00-0.25 First two syncytial divisions occur. Embryo dark in center, lighter at periphery, due to distribution of yolk granules
2 0.25-1.50 Syncytial divisions 3-8, separation of egg cytoplasm from envelope Two empty spaces appear at either pole
3 1.50-1.20 Syncytial division 9, polar buds formed in posterior space Clear cytoplasmic ring around periphery of embryo
4 1.20-2.10 Syncytial division 10-13. Polar buds increase in number Appearance of somatic buds in periphery of embryo due to location of blastoderm nuclei
5 2.10-2.50 Cellularisation begins, anterior space disappears Pole cells move dorsally, blastoderm nuclei elongate
6 2.5-3.00 Onset of gastrulation, ventral and cephalic furrows form Pole cells shift dorsally. Blastoderm cells shift position forming dorsal plate
7 3.00-3.10 Completion of gastrulation Three dorsal folds become visible as a result of endoderm invagination. Pole cells no longer visible on surface
8 3.10-3.40 Germ band expansion Formation of amnioproctodeal invagination
9 3.40-4.20 Stomodeal cell plate formation, continuation of germ band expansion Clear layering of germ band due to delamination of neuroblasts. Anterior pole separates from vitelline envelope
10 4.20-5.20 Germ band expansion ceases Invagination of stomodeum, parasegmental grooves appear
11 5.20-7.20 Apoptosis begins. Germ band retraction initiates Segmental furrows become apparent. Tracheal pits and malphigian tubules form
12 7.20-9.20 Germband retraction Anterior, posterior midgut fuse. Yolk sac moved dorsally. Tracheal tubes fuse together. Ventral cord separates form epidermis
13 9.20-10.20 Germ band retraction completes. Head involution begins. Yolk sac protrudes dorsally, labium moves to midline on ventral side
14 10.20-11.20 Head involution continues Dorsum, and midgut begin closing. Dorsal spiracles become evident
15 12.20-13.00 Epidermal segmentation completed. Head involution continues Epidermis and gut close completely
16 13.00-16.00 Intersegmental groves visible at mid-dorsal levels Four gastric caecae evaginate from midgut
17 16.00 until hatching Air infiltrates tracheal tree. Movement of embryo visible within viteline envelope Ventral cord continues retraction

History of Drosophila Embryological Model Use

  • Ectomologist Charles W. Woodworth was the first to breed the Drosophila at Harvard university and suggested to W.E. Castle they could be used in studies of genetics.
  • In 1908 T.H Morgan, an American geneticist and embryologist, was looking for an inexpensive that could be breed quickly and in limited space and Castle suggested the drosophila. Through Morgan’s studies of heredity he discovered the white-eyed mutation in the drosophila.
  • By 1910, at Columbia University T.H Morgan and his students work on the top floor of the Schermerhorn Hall and t became known as the fly room. Students of the Fly Room were A.H. Sturtevant, C.B Bridges and H.J. Muller.
  • In 1913 Sturtevant published a paper with the first genetic map and clearly laid out the logic for genetic mapping.
  • In 1927 Muller ionized radiation and found it caused genetic damage.
  • 1930’s feasability of generating deficiences and duplications were exploited in 1970 to generate duplicates and initiating whole-genome scanning.
  • In 1933 Morgan won the Nobel Prize for his discovery that genes are carried on chromosomes and are the mechanical basis of hereditary.
  • Also in 1933 Heitz and Bauer fly Bibio hortulanus studies discovered salivary gland chromosomes.
  • 1934 saw the 1st published drawings of Drosophila melanogaster polytene chromosomes by T.S painter.
  • In 1935 and 1938 Bridges publish polytene maps that are still used today.
  • In 1946 Muller received the Nobel prize for his work, showing mutation induced by x-rays.
  • In 1972 D.S. Hogness of Stanford Universtiy put in a grant application for modern genome reseach and in 1974 he made the 1st random clone of any organism.
  • In 1975, clone libraries representing the entire genome had been generated and screened for clones carrying specific sequences.
  • In 1980 C. Nusseiln-Volhard and E. Wieschaus attempt to identify all genes involved fundamental processes leading to the discovery of major signalling pathways. In 1995 they shared a Nobel Prize for their work.
  • In 1981 a breakthrough of first rescue of a mutant phenotype in an animal by gene transfer. This led to the use of enhancer traps to screen for genes based on pattern of expression.
  • In 2000 the Drosophila melanogaster genome was published.


Genetics of Drosophila

The Drosophila melanogaster fly has four pairs of chromosomes: the X/Y sex cells and the autosomes 2, 3 and 4. The fourth chromosome is so small that it is usually overlooked. The comparison of the insignificant 4th chromosome to the other three pairs are shown in the image to the right.

The size of the Drosophila genome is about 165 million pairs and estimated to contain about 14000 genes. In comparison, humans have 3.4 billion base pairs with about 22500 gene sequences and yeast has about 5800 genes in 13.5 million base pairs.

Also a good link to a variety of info: http://ceolas.org/VL/fly/index.html



Current Embryology Research on Drosophila

Links

http://flybase.bio.indiana.edu/ This site is a database for anything Drosophila related. It contains an exceptional image and movie catalogue which can be very helpful.

http://www.sdbonline.org/fly/aimain/1aahome.htm The Interactive Fly has a lot of information of the embryogenesis, pupal development and larval devlopment of Drosophila

References

1. Campos-Ortega, Hartenstein (1985) The Embryonic Development of Drosophila melanogaster. Springer-Verlag berlin Heidelberg. pp9-84


2. Katrin Weigmann, Robert Klapper, Thomas Strasser, Christof Rickert, Gerd Technau, Herbert Jäckle, Wilfried Janning and Christian Klämbt: FlyMove – a new way to look at development of Drosophila.Trends Genet. In press. http://flymove.uni-muenster.de


3. Sturtevant, A. H. 1913. The linear arrangement of six sex-linked factors in Drosophila, as shown by their mode of association. Journal of Experimental Zoology, 14: 43-59.


4. A brief history of Drosophila's contributions to genome research. Rubin GM, Lewis EB. Science. 2000 Mar 24;287(5461):2216-8. PMID: 10731135


5. Drosophila melanogaster: A case study of a model genomic sequence and its consequences,

  1. Michael Ashburner2 and
  2. Casey M. Bergman1
PMID: 16339363 


ANAT2341 group projects

Project 1 - Rabbit | Project 2 - Fly | Project 3 - Zebrafish | Group Project 4 - Mouse | Project 5 - Frog | Students Page | Animal Development