Lab 1: Introduction to Drosophila

Heredity & Human Affairs, BIO-1605
Drosophila melanogaster
 Scientific name: Drosophila melanogaster

(must be italicized or underlined, written text)
 Common name: “fruit fly”
 Characteristics of “normal” WILD-TYPE:

Wings, for flight
Red eyes

Observe fly vial – note these characteristics

Female vs. Male
e
Female
•Less banding at tip of abdomen
Sex combs
Male
•Darker banding on abdomen (darker
butts!)*
*Exception: young males may have
underdeveloped band coloring & may appear
similar to females.
•ALL males have SEX COMBS on forelimbs.
Drosophila Life Cycle
*SEE BACK COVER OF CAROLINA DROSOPHILA MANUAL.
 Egg: very small white;
may be seen stuck to tip
of female’s abdomen
 Larva: “maggots” – will
be found eating blue
culture media/food
 Pupa: growth stage –
will turn dark just before
adults emerge.
 Adults: common fruit
fly (as seen in lab)
/egg
Fun Fact of the
Day!
Fruit Flies Have Been Studied in
Space by NASA!
One small
step for fly,
one giant
flight for fly kind
Fun Facts about Drosophila!
 Fruit flies = most studied modeled organisms in the
world





Quick lifecycle (females will mate 8-12 hrs after emergence)
4 pairs of chromosomes
Lots of mutations
Share similar characteristics = sleep deprivation and learning
About 61% of known human disease genes have a recognizable
match in the genetic code of fruit flies.
Culturing Techniques
*TA will demonstrate .
*SEE CAROLINA DROSOPHILA MANUAL.
 Mix 1:1 ratio of Formula 4-24 Blue, culturing media (food), &
water in a clean fly vial.
 All to sit out to dry without sponge cap.
 Add 3 – 5 grains of yeasts. Do not add more yeast…it will kill
your flies (CO2 poisoning).
 Carefully, anesthetize the adult flies using FLYNAP.
 Wear gloves. TA will DEMO.
 Place sleeping flies on index card & observe with dissecting
microscope.
 Use paintbrush to carefully separate males and females.
 To set up a cross: add ~4 males + ~4 females to each new
culture vial.
Name: J. Reid + K. Riggan
 Keep vial on its side until flies awaken. Otherwise,
Section: 001 (AM lab)
they get stuck in the food
Date: 1/17/2012
 Label your new culture vial!
P1: 4
(+,+) x 4
(ap, ap)
THESE FLIES ARE YOUR BABIES!
Genotypes vs. Phenotypes
GENOTYPE
PHENOTYPE
•The genetic make-up of an
individual.
•The physical expression of
those genes.
•The genes (alleles)
•The traits
Example:
Example:
Wild-type fly
Genotype = (+, +)
Wild-type fly
Phenotype = winged, redeyes (“normal”)
Drosophila Normal vs. Mutants
“NORMAL”
Dominant
or Recessive?
Human
Examples
Genotype(s):
Phenotype:
Mutation:
(wild-type)
WING
MUTATION
(apterous)
EYE
MUTATION
(white-eyed)
Dominant
Trait
Autosomal
Recessive
Sex-Linked
brown eyes, dark Tay-sachs, cystic Hemophilia, colorhair
fibrosis
blindness
(+, +) or (+, ?)
(ap, ap)
(Xw, Xw) or XwY
“normal” fly
with normal
wings & red eyes
Wingless fly
White eyes
(Note: has red eyes)
(Note: has normal wings)
None
Chromosome #2
Chromosome #1
(sex chromosome in flies)
Pictures:
Chromosomes
*SEE PAGE 23 OF CAROLINA DROSOPHILA MANUAL.
 Drosophila have 4 pairs of chromosomes, 8 total.
 Chromosomes 2 – 4 are autosomal.
 One pair = sex chromosomes (Chr #1)
 Humans have 23 pairs of chromsomes, 46 total.
 Chromosomes 1 – 22 are autosomal.
 One pair = sex chromosomes (Chr #23, X or Y)
Chromosomes
*See also page 23 of the CAROLINA DROSOPHILA MANUAL.
Fly Generations
P1: Parental Generation (parents)
F1: First Filial Generation (kids)
F2: Second Filial Generation (grandkids)
Based on Mendelian Inheritance Patterns you should be able
to predict the genotypic & phenotypic ratios of the F1 & F2
offspring.
Set up a Punnett Square
Examples to try on the board:
P1 generation: You cross (+,+) females X (ap, ap) males
P1 generation: You cross a white-eyed female X wildtype males
What are the predicted genotypic & phenotypic ratios
of the F1 generation?
What are the predicted genotypic & phenotypic ratios
of the F2 generation?
Punnett Squares –
F1 + F2 predictions, Wing Mutants
Wing
mutation
ap
ap
Wing
mutation
+
ap
+
+
F2’s
F1’s
+
F1 generation=
Genotypic ratio: 100 % (+, ap)
ap
F2 generation=
Genotypic ratio:
1 (+,+) : 2 (+,ap) : 1 (ap, ap)
Phenotypic ratio: 100% winged
Phenotypic ratio:
3 winged : 1 wingless
Punnett Squares –
F1 + F2 predictions, White-Eyed Mutants
Eye
mutation
X+
Y
Eye
mutation
Xw
Y
X+
Xw
F2’s
F1’s
Xw
F1 generation=
Genotypic ratio: 1 X+Xw : 1 Xw Y
Phenotypic ratio:
100% females red-eyed;
100% males white-eyed
Xw
F2 generation=
Genotypic ratio:
1 (X+Xw) : 1 (XwXw) : 1 (X+ Y) : 1 (Xw Y)
Phenotypic ratio:
1 red-eyed female : 1 white-eyed female :
1 red-eyed male : 1 white-eyed male
•Get to know your flies!
•A. Observe wild-type, apterous & white-eyed
•B. Observe Life Stages (have instructor sign-off)
•C. Observe males & females -record #’s/ratios.
•D. Record observations & data in lab packet.
•Practice Culturing Techniques – your flies must
survive (we will check them next week)!
•Mate 3 sets of flies, if available (work in pairs)
•A. Cross wild x apterous: (+, +) x (ap, ap)
•B. Cross wild x white-eyed female: (+, +) x (Xw, Xw)