Introduction into Drosophila Flashcards

1
Q

Why is it useful to use a model organism that has been used many times before?

A

Lots of information of it (background knowledge) from previous studies

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2
Q

What are the advantages of using the drosophila as a model organism?

A
  • Accessible embryology
  • Accessible adult stages that are WELL DEFINED
  • Low cost
  • Fast generation time
  • Excellent genetics
  • No ethical concerns
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3
Q

What are the disadvantages of using the drosophila as a model organism?

A

Not a vertebrate (lacks features of a vertebrate)

Kept as live stocks

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4
Q

Describe the life cycle of the drosophila

A

1) Fertilised egg undergoes cleavage –> syncytial blastoderm
2) Gastrulation - form embryo with 3 layers \
3) Embryo hatches - first instar larvae
4) 2nd instar larvae
3) 3rd instar larvae
4) Larvae to pupa
5) Metamorphosis to adult fly

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5
Q

How long after fertilisation does it take the drosophila egg to become a syncytial blastoderm?

A

3 hours

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6
Q

What does the drosophila larvae contain/do?

A

Contains many digestive organs, gut and glands

Builds up energy sources

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7
Q

When does the larvae become pupa?

A

6-7 days after laying

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8
Q

What happens during the larvae to pupa stage?

A

Skin hardens and larvae skin dissolves

Adult tissue comes out of the larvae and forms the adult body shell

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9
Q

Where is the adult body tissue of the fly made?

A

In the larvae

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10
Q

What does the energy stores laid down by the larvae help?

A

Helps to shape metamorphosis

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11
Q

What is fascinating about drosophila courtship?

A

It is the STRONGEST and most REPRODUCIBLE behaviour

It is GENETICALLY ENCODED (how to act and respond)

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12
Q

Describe the structure of the drosophila penis

A

Tip of the testies contains the HUB

Hub is surrounded by STEM CELLS

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13
Q

What do the stem cells do in the drosophila penis?

What happens at the same time?

A

They divide

Each time divide:

  • Cell closest to the hub maintains STEM CELL fate
  • Cell furthest away DIFFERENTIATES into a CYST
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14
Q

What does the cyst in drosophila give rise do?

A

Cluster of spermatids

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15
Q

How does the cell closest to the hub maintain stem cell fate?

A

The hub secretes factors that maintain the fate:

  • Unpaired
  • JAK/STAT pathway
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16
Q

What do the ovaries of drosophila contain?

What are these?

A

Ovarioles

Where the egg develops from a stem cell

17
Q

When are drosophila eggs fertilised?

How?

A

Immediately before they are laid

By sperm that is stored in the SEMINAL RECEPTACAL

18
Q

Describe the structure of ovarioles

A

‘Time line’ of egg development in egg chambers:

  • Start with stem cells that are maintained with JAK/STAT signalling
  • Cells leave stem cell niche to start to differentiate
  • These cells form a group of cells that ultimately give rise to a group of cells where one will become the EGG and the other will become the NURSE CELLS
19
Q

What are ‘nurse cells’?

How do they do this?

A

Support cells that nurture and feed the egg (with yolk, proteins)

Do this by duplicating their DNA massively in order to make the supplies (maternal cotributions)

20
Q

What are polytene chromosomes?

When do they occur?

What do you end up with?

A

Giant chromosomes

Occur when the DNA is duplicated but isn’t separated into 2 separate cells

Occurs in the nurse cells many many times

End up with MANY sets of DNA lying parallel to each other

21
Q

How are the maternal contributions of the nurse cells moved into the developing egg?

A

Through cytoplasmic dumping through ring canals

22
Q

What are ring canals?

A

Physical holes between the nurse cells and the egg

23
Q

What happens do the nurse cells once they have performed cytoplasmic dumping?

A

They shrivel up and die

24
Q

How are some maternal factors localised?

A

Actively by microtubule transport

25
What is the structure of the egg?
Chorion (egg shell) Vitelline membrane (underneath the chorion)
26
What is the function of the vitelline membrane?
It is hydrophobic - prevents the egg from drying out
27
Where is the chorion secreted from?
Follicle cells
28
What happens once the egg is laid?
1) Pronuclei fuse to make a diploid organism 2) Nucleus formed divides 14 times (WITHOUT CELL DIVISION) 3) After the 14th division - the nuclei move to the outside of the cell and pauses 4) Membranes grow up from the outside into the yolk and forms many cells
29
How do the nuclei undergo 14 divisions without cell division?
Using the materials laid down by the mother in the nurse cells