Genetics
Drosophila melanogaster
OR
The Fruit fly labs
Why Use the Fruit fly
 Drosophila melanogaster is the classic
laboratory organism for genetic study
 These small flies are called fruit flies, pomace
flies, or vinegar flies.
 They are inexpensive, quickly reared in the lab
( life cycle in 10-14 days at room temperature
but grow best at 25 C), have simple food
requirements, take up little space and contain
many mutant strains that are easily identified.
Charateristics
 Like all insects,
Drosophila have 3 main
body parts: head, thorax
and abdomen.
 The major structures on
the head are the large red
(unless mutated)
compound eyes.
 The thorax has six legs,
and two wings

LIFE
CYCLE
 Drosophila go through
four stages in their
lives, which take
about 10-14 days to
complete.

Stage 1: Egg
 Egg: eggs are laid by
female on the food
and take about 1 day
to hatch.
Stage 2: Larval stage
 Larval
stage: these
are the
maggots,
which crawl
through the
food, eating as
they go. This
stage lasts
about 7 days
Stage 3: Pupae
 Pupae: these are
the cocoons in
which the larvae
metamorphose into
adults. This stage
lasts 5 days.
 During the last day
the eyes and dark
wings can be seen
forming inside.
Stage 4: Adult
 Adults: Emerges
from the pupal case
white and elongated
with wings still
folded up. After
about 1 hour the
wings expand. After
8-10 hours the
adults are sexually
mature.
Fly Separation
 Flies have no morals!! If there is a male
around, the female will become pregnant.
 Once a female has mated she stores
enough sperm to fertilize all her eggs for
life.
 To ensure controlled mating, it is important
to use virgin female flies. Thus one must
sex and separate the males from female
flies and store them in separate vials.
Flynap
 To examine flies, they need to be immobilized or
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
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they will fly away.
We will be using flynap to immobilize our flies.
Place the flynap wand in the vial for about a
minute, the flies will begin to fall asleep
While flynap is safe for flies, over anesthetizing
flies could be fatal.
When done looking or sorting the flies, put the
flies back in the vial, but not on fresh food. If the
food is verywet or loose, the flies can drown.
Determining the sex of flies
 Color and shape of abdomen are not
reliable for sexing newly emerged adults.
 Use the sex combs located on the front
legs of the male to differentiate between
male or female.
 Also remember that when first hatched,
the female hatch before the males, so you
may not have a 1: 1 male, female ratio
Sex combs of a male fly
Female Fly
Drosophilia Facts
 Drosophilia flies only have 4 chromosomes.
 During the course of this class, we will be performing:
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monohybrid crosses, dihybrid crosses and sex-linked
crosses.
A Monohybrid cross is a cross involving two parents,
who differ in the expression of a single heritable trait.
A dihybrid cross is a cross involving parents, who differ
in the expression of two heritable traits.
Monohybrid and Dihybrid crosses can be performed
using genetic traits located on chromosomes 1,2, 4.
Sex-linked crosses contain traits that are controlled by
genes located on the sex chromosomes ( chromosome
#3).
Wild Type (Normal Flies)
Apterous Flies
(no wings)

Vestigial (wings reduced)
Bar eyed
(narrow eyes)( sex-linked)
Sepia eyes
( eyes brown and change to black as fly ages)
White eyes
Curly wings