Getting to know Drosophila
melanogaster
RS: Maribel Alvarez
Nelida Rojas, Santa Ana High School
http://grad.bio.uci.edu/dc/alvarezM/Maribel
_Alvarez/Welcome.html
maribea@uci.edu
Arora Lab
QuickTime™ and a
decompressor
are needed to see this picture.
Presentation Outline
• Introduction to Drosophila melanogaster.
• Station 1: Identify the different stages of
Drosophila development. (week 1)
• Station 2: Identify males versus females. (week2)
• Station 3: Flying through genetics. (week 3)
• Station 4: Gene expression, function, and
regulation. (week 4)
Drosophila Melanogaster, a
popular genetic model organism
• ~ 50% of fly genes
have vertebrate
homologs.
• Small and easy to
grow in lab.
• Short life cycle.
• Produce high
amounts of offspring.
QuickTime™ and a
decompressor
are needed to see this picture.
Drosophila Melanogaster is used to study
the biological processes underlying:
• Embryonic
development
• Neurodegenerative
disorders
• Diabetes
• Aging
• Drug abuse
• Cancer
QuickTime™ and a
decompressor
are needed to see this picture.
Station 1: Identify the different stages of
Drosophila development
The life cycle of Drosophila melanogaster
Station 1: Identify the different stages
of Drosophila development
• The egg: Eggs are small, oval
shaped, and have two filaments at
one end.
•The larval stage: The larva look like
worms. They use black mouth
hooks to eat. Three larval stages.
• The pupal stage: A pupa
undergoes four days of
metamorphosis. They form a hard
and dark pupal case.
• The adult stage: Adult flies have a
head, thorax, abdomen, six legs,
and two wings. They live a month or
more and then die. A female does
not mate for 10-12 hours after
emerging from the pupa.
Station 2: Identify males
versus females
1. Size of adult The female is larger than the
male.
2. Shape of abdomen The female abdomen
curves to a point; the male abdomen is round
3. Markings on the abdomen Alternating dark
and light bands can be seen on the entire
rear portion of the female; the last few
segments of the male are fused.
4. Appearance of sex comb On males there is
a tiny tuft of hairs on the front legs.
5. External genitalia on abdomen Located at
the tip of the abdomen, the ovipositor of the
female is pointed. The claspers of the male
are darkly pigmented, arranged in circular
form, and located just ventral to the tip.
sex comb
QuickTime™ and a
decompressor
are needed to see this picture.
Is this a female or male?
This is a virgin female. In genetic experiments, it
is important that the female be a virgin in order to
determine genetic background of progeny.
Station 3: Flying through genetics
• Humans are diploid organisms (2n)
• Humans have 23 pairs of chromosomes
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
Station 3: Flying through genetics
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
• Mendel’s law of segregation states that during
gamete formation the pair of alleles segregate so
that each gamete only gets one allele
Station 3: Flying through genetics
Drosophila is a diploid organism (2n)
Female
Male
XX /XY
Sex
II
III
IV
-----------Autosomal-----------
QuickTime™ and a
decompressor
are needed to see this picture.
Station 3: Flying through genetics
• To study the basic genetic
principles of mendelian
inheritance a cross has been
set up between male flies
that have Curly (Cy) wings
and a wild-type virgin
female flies with straight
wing (Cy+). Cy is a
dominant trait.
Station 3: Flying through genetics



You have been given a vial with both female and male flies.
Put the flies to sleep using FlyNap in the classroom. Today we will use CO2.
Count the number of females and males. Record you results in the following
table:
Station 4: Gene expression, function, and
regulation
The development and growth of an organism is greatly
dependent on the proper expression of genes
QuickTime™ and a
decompressor
are needed to see this picture.
Gene Expression
Station 4: Gene expression, function, and
regulation
• All cells have the
same genetic
information however
only specific genes are
turned on or expressed
in each cell type
QuickTime™ and a
decompressor
are needed to see this picture.
Gene Expression
Organisms need genes expressed in specific cells at the right time. Gene
expression must be regulated for proper growth and development of organisms
Station 4: Gene expression, function, and
regulation
1. What would happen if
the neuron specific gene
is not expressed in cell
one?
No neuron
2. What would happen if
the neuron specific gene
was expressed instead
of the epithelial specific
gene in cell 2?
The cell that was suppose to be an
epithelial cell would be a neuronal cell.
1.
2.
QuickTime™ and a
decompressor
are needed to see this picture.
Station 4: Gene expression, function, and regulation
We will study the function and expression of eyeless (ey), a gene
responsible for making eyes in Drosophila.
QuickTime™ and a
decompressor
are needed to see this picture.
QuickTime™ and a
decompressor
are needed to see this picture.
?
Station 4: Gene expression, function, and regulation
ey is expressed in the larval eye disc, which
develops into the adult eye.
QuickTime™ and a
decompressor
are needed to see this picture.
Station 4: Gene expression, function, and regulation
How do we study gene expression?
Qui ckT ime™ and a
dec ompress or
are needed to s ee this pic ture.
eyeless promotor
eyeless gene
eyeless promotor
Reporter: GFP or LacZ
Station 4: Mutations affecting gene
expression
We have altered the expression of ey in flies found in vials 2
and 3. Observe and record their phenotypes.