Drosophila melanogaster By: Jen

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Drosophila melanogasterBy Jen Bo
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Structure and Organization of genome

• Genome is about 5 of the human genome in size
• 13,600 genes
• 4 chrms where chrm 1 is the X chrm, and chrms
  2-4 are autosomes
• Female XX Male XY where Y plays no role in
  determination of a male, but the ratio of the
  of Xs

• Low chrm number is a key advantage for genetic
  studies because it simplifies most genetic
  manipulations
• Polytene chrms (giant chrms that have many
  identical chromatids) allow efficient mapping of
  the fly genome since they only contain small
  amount of DNA

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Life Cycle

• Very detailed life cycle
• Takes appox. 10 days from fertilization to
  emergence of adult fly (25 C)
• A female can produce 3000 progeny in her
  lifetime the male can have over 10,000 offspring
  
• Embryo develops into first, second, and third
  instar and then into the pupal case

• Metamorphosis Disintegration of larval tissues
  and their replacement through the proliferation
  and differentiation of cells (reorganization of
  flys body plan)
• Most structures including the eyes, wings, legs,
  genitalia generate from the imaginal discs
  (D.5)

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Techniques of Genetic Analysis

• Crossing over occurs only in females making it
  possible to maintain linkage relationships
• Balancer chrm are used to allow mutations to be
  carried onto progeny w/o changes from crossing
  over (D.6)

• P-elements act like vectors to introduce clone
  DNA into the organism (inject the ends w/o the
  transposase coinject the transposase w/o the
  ends) D.8
• P elements once inside allow geneticist to track
  a gene of interest through progeny

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Techniques continued

• Once a P insertion is found, plasmid rescue can
  be performed (D.9)
• A powerful way to detect genes that are turned on
  in specific tissues is through enhancer trapping
  (identification of P-element insertion lines
  w/B-galactosidase patterns)

• Lineage compartments are variations of the same
  body part
• Genetic mosaics can be created to determine the
  pathway of the compartment

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Mosaic Analysis

• Mosaic analysis can be used to follow genes of
  interest
• Mitotic recombination is used to produce clones
  of cells homozygous for a mutation allowing the
  flies to reach adulthood

• The use of FLP and heat shock to allow
  recombination to occur resulting in high
  frequency of clones and several clones on each
  fly

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Ectopic Expression

• Expression outside the cells or tissue where the
  gene is normally expressed

• GAL4 method highly versatile tool for studying
  Drosophila development due to the large number of
  enhancer trap lines expressed in many different
  patterns

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Drosophila Genome Project

• We share 61 of genes w/homologs in the fly
• Flies only have one copy of genes making
  mutations more easier noticeable

• Future Goals isolate P-element insertional
  alleles of as many genes as possible
• Different knockout techniques most efficient to
  eliminate different functions of genes

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The End
Questions?