Introduction to Drosophila Techniques & P1 x P1 Matings
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 Sex combs
Female •Less banding at tip of abdomen
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)
Culturing Techniques *TA will demonstrate . *SEE CAROLINA DROSOPHILA MANUAL (Culturing pg 4-8, Anesthetizing pg 9) •
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. 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 of the same ‘type’ to each new culture vial. Name: B. Reo & J. Jamison – Keep vial on its side until flies awaken. Otherwise, Section: 001 (Tues AM lab) they get stuck in the food
Label your new culture vial!
(+,+) x 5
Genotypes vs. Phenotypes GENOTYPE
•The genetic make-up of an individual.
•The physical expression of those genes.
•The genes (alleles)
Wild-type fly Genotype = (+, +)
Wild-type fly Phenotype = winged, red-eyes (“normal”)
Drosophila Normal vs. Mutants “NORMAL”
WING MUTATION (apterous)
EYE MUTATION (white-eyed)
brown eyes, dark hair
Tay-sachs, cystic fibrosis
(+, +) or (+, ?)
(Xw, Xw) or XwY
“normal” fly with normal wings & red eyes
(wild-type) Dominant or Recessive? Human Examples
has red eyes)
(Note: has normal wings)
Chromosome #1 (sex chromosome in flies)
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 (X+,Y) males X (Xw, Xw) females What are the predicted genotypic & phenotypic ratios of the F1 generation? (pages 9 & 10) One step further: What are the predicted genotypic & phenotypic ratios of the F2 generation?
Punnett Squares – F1 & F2 predictions, Wing Mutants P generation: +,+ x ap,ap Wing mutation
F1 generation: +,ap x +,ap Wing mutation
+ ap F2’s
F1 generation= Genotypic ratio: 100 % (+, ap) Phenotypic ratio: 100% winged
F2 generation= Genotypic ratio: 1 (+,+) : 2 (+,ap) : 1 (ap, ap) Phenotypic ratio: 3 winged : 1 wingless
Punnett Squares – F1 & F2 predictions, White-Eyed Mutants P generation: XwXw x X+Y Eye mutation
F1 generation: XwX+ x XwX+ Eye mutation
F1 generation= Genotypic ratio: 1 X+Xw : 1 Xw Y Phenotypic ratio: 100% females red-eyed; 100% males white-eyed
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
Today’s General Plan: •Get to know your fly babies! •A. •B. •C. •D.
Observe wild-type, apterous & white-eyed phenotypes. Observe Life Stages (have instructor sign-off), page 7 Observe males & females. Count flies in 1 vial. Record observations & data in lab packet, page 7
•Predict F1 offspring:
•A. Set up P1 x P1 Punnett Squares, pages 9 & 10
NEXT WEEK! • QUIZ #1 on this lab material.
• Lab #3: Human Inherited Traits • Check Fly Matings – Clear/Re-do P1 x P1 Matings