Term
| What is the life cycle of Drosophila? |
|
Definition
Takes 10 days at 25°.
An adult produces an embryo.
1st, 2nd and 3rd instar larvae stage.
The forms a pupa and then an adult. |
|
|
Term
| What are the Drosophila femal ovaries like? |
|
Definition
Ovary is stem of ovarioles (like beads on a string) and each of these contains an oocyte.
Each oocyte is surrounded by small follice cells on the posterior end (these encase the oocyte in the shape of a C). On the anterior end there are large nurse cells (these take up half the mass), inbetween these and the oocyte there are a small bundle of border cells. |
|
|
Term
| Explain Sander's first experiment. What did it prove? |
|
Definition
When the egg is pricked at the anterior end allowing some cytoplasm to escape the resulting laval head structures are reduced.
This showed us that there was a relation between the cytoplasm in the egg and the structures formed in the larva. |
|
|
Term
| Explain the experiments that confirm the importance of cytoplasmic determinants upon development. |
|
Definition
When cytoplasm from the anterior end of one egg is injected into the posterior end of another egg only head and thorax segments develop.
When cytoplasm from the posterior end of one egg is injected into the anterior end of another egg only abdominal segments arise.
Proves cytoplasm form different regions of the egg have different properties. |
|
|
Term
What was the Heidelburg experiment?
(The basics- not the genes involved) |
|
Definition
They selected 5,000 candidate genes for pattening and mutated each of them four times (using 20,000 scores (just incase some didn't work due to silent mutations etc.)).
They then crossed the flies so they could get flies homozygous for the mutation. Doing this they discovered that pattering genes are inherited maternally.
They then analysed the cuticles and denticle patterns of the flies to see how the patterning had changed. |
|
|
Term
| What do the maternal genes do? What ones are there? |
|
Definition
There is cytoplasmic polarity of the genes mRNA in the egg before fertilization (A simple increase in mRNA at one end and then decreasing at the other).
The genes bicoid and hunchback regulate the formation of anterior structures. Caudal and nanos regulate the formation of posterior parts of the embryo. |
|
|
Term
| What do the gap genes do? What ones are there? |
|
Definition
Their transcription is triggered by the maternal genes- they form three broad, overlapping bands.
There is hunchback, kruppel, knirps, giant and tailess. |
|
|
Term
| What do bicoid and hunchback do? |
|
Definition
| Cause the formation of anterior structures. |
|
|
Term
| What do the pair-rule genes do? What ones are there? |
|
Definition
Differeing concentrations of the gap genes cause the transcription of the pair-rule genes.
These divide the embryo into seven bands perpendicular to the A/P axis.
These are even-skipped, odd-skipped, hairy, runt, fushi-tarazu and paired. |
|
|
Term
| What do the segment polarity genes do? What ones are there? |
|
Definition
The pair-rule genes activate the transcription of the segment polarity genes that split the segments in half forming 14-segment wide units.
These are engrailed and wingless. |
|
|
Term
| What do the homeotic selector genes do? |
|
Definition
| The combination of the gap, pair-rule and segment genes causes the transcription of these genes. their purpose is to detemine the developmental fate of each segment. |
|
|
