L6 - Introduction to Drosophila

Question 1

Positives of mice as animal models?

Answer 1

Good genetics

Well established model

Question 2

Negatives of mice as animal models?

Answer 2

Expensive
Slow reproductive cycle
Ethical restrictions/home office

Question 3

Positives of chicks as animal models?

Answer 3

Accessible embryology

Low cost

Question 4

Negatives of chicks as animal models?

Answer 4

No genetics

Ethical restrictions/home office

Question 5

Positives of zebrafish as animal models?

Answer 5

Accessible embryology

Reasonable low cost

Question 6

Negatives of zebrafish as animal models?

Answer 6

Genetics problematic

Ethical restrictions

Question 7

Positives of drosophila as animal models?

Answer 7

Accessible embryology and adult developmental stages 
Very low cost 
Fast reproductive cycle 
Good genetics 
No ethical restrictions

Question 8

Negatives of drosophila as animal models?

Answer 8

Not a vertebrate

Kept at live stocks

Question 9

Drosophila life cycle

Answer 9

Live around 60 days
Life cycle
- 10 days at 25oC
- 21 days at 18oC

Question 10

Drosophila life cycle stages

Answer 10

1. Fertilised egg (cleavage)
2. Syncytial blastoderm (gastrulation)
3. Embryo (hatching)
4. Larva
5. Pupa (metamorphis)
6. Adult fly

Question 11

Drosophila history - 1910

Answer 11

Morgan discovered a white eyed fly

Question 12

Drosophila history - 1913

Answer 12

Sturtevant constructed first genetic map - genes arranged in a linear order

Question 13

Drosophila history - 1914

Answer 13

Bridges showed that chromosomes must contain genes

Question 14

Drosophila history - 1927

Answer 14

Muller showed that X-rays cause mutations and chromosomal rearrangements

Question 15

Drosophila history - 1980

Answer 15

Christiane Nüsslein-Volhard and Eric Wischaus undertook a saturation mutagenesis to identify genes involved in development and patterning of larval cuticle

Question 16

Drosophila history - 1980s

Answer 16

Technical and methological advances

• P-element transformation - transgenics
• Enhancer trap - promoter trapping
• Gal4/UAS - gene misexpression
• FLP/FRT - clonal mutant analysis
• RNAi - ex vivo and in vivo
• ‘omic’ technologies - genome, transcriptome, proteome

Question 17

Drosophila history - 2014

Answer 17

Drosophila melanogaster genome release 6

• 143 million bp
• 137.6 million bp on the 7 chromosome arms
• Remaining gaps of around 1.5Mbp all in heterochromatin regions

Question 18

Drosophila melanogaster ptp61F - a tyrosine phosphatase sequence was compared to?

Answer 18

Drosophila simulans - 3.4 my
Drosophila erecta - 6.8 my
Drosophila ananassae - 9.5 my
Drosophila pseudoobscura - 23.7my
Drosophila virilis	- 34.5my  
Protein encoding exons are conserved – don’t  diverge as quickly

Question 19

How many offspring can flies produce in roughly 2 weeks?

Answer 19

Around 200

Question 20

How is Drosophila courtship passed down generations?

Answer 20

Strong reproducible behaviour
Genetically encoded (not learned)

Question 21

What are some examples of Drosophila courtship?

Answer 21

Orientation 
Tapping 
Wing vibration 
Licking 
Attempted copulation

Question 22

In flies what does the testes consist of?

Answer 22

Consist of hub cells
Stem cells located adjacent to hub
Cells further away differentiate

Question 23

What do Hub cells secrete?

Answer 23

Unpaired - JAK/STAT pathway ligand

Question 24

Oogenesis

Answer 24

Females only need to mate once in lifetime
Seminal receptacle stores sperm
Eggs drilled into food when laid

Question 25

How are stem cells maintained in the embryo?

Answer 25

``` 4x incomplete cystoblast mitotic divisions Selection of future oocyte - Nurse cells - endo-reduplication - Oocyte - Diploid nucleus - Meiotic recombination ```

Question 26

What does the fly sperm fuse with?

Answer 26

The female pro-nucleus

Question 27

What is the function of nurse cells?

Answer 27

They are support cells | Supply egg with protein, yolk, RNAs - maternal contributions

Question 28

How are the maternal contributions from nurse cells transferred into oocyte?

Answer 28

Transferred into developing oocyte via cytoplasmic dumping | Occurs via ring canals

Question 29

How are nurse cells replicated?

Answer 29

Endo-reduplication - DNA replication without cytokinesis Many copies of the genome

Question 30

What are polytene chromosomes?

Answer 30

``` All sister chromatids lie together Bands - little gene activity Interbands - active genes Puffs - extremely active gene 5000 bands - each 22 kb ```

Question 31

Microtubule transport is used to?

Answer 31

Aid subcellular localisation - Minus and plus ended motors - Glue anchors them in position

Question 32

What is chorin?

Answer 32

Egg shell | Secreted by the follicle cells

Question 33

What is the vitelline membrane?

Answer 33

Hydrophobic | Protects from drying out

Question 34

What does early development via nuclear divisions look like?

Answer 34

Nucleus replicates DNA with no cell division | Uses maternal material form nurse cells

Question 35

What happens after the 14th nuclear division?

Answer 35

Membranes grow from outside and each nucleus gets pinched of into its own cell