Drosophila body plan Flashcards
Who did the first mutagenesis screens in flies?
Christane Nusslein and Eric Wischaus
What is the phenotype in a knirps mutation?
Knirps = little boy in german
They have a shorter middle segment in the larvae
What is the phenotype of a gooseberry mutation?
Half of each segment is missing
What is the order in which genes are controlled in fly development?
Maternal genes -> Gap genes -> Pair rule genes -> Segment polarity genes
What is bicoid?
A DNA binding transcriptional activator
Maternally loaded into the developing oocyte
Has roles in anteriorisation eg in head formation
What happens if bicoid is placed in the middle of a bicoid mutant egg?
A mirror image of the thoracic segment will form if bicoid is placed in the middle of the mutant egg
Low affinity bicoid binding sites need what to be activated?
High levels of bicoid
Where are low affinity bicoid binding sites likely to be found?
In the head structures
What is the role of the gap genes?
To control pair rule genes
List examples of gap genes?
Hunchback, Giant, Kruppel, Knirps and tailless
Mutations in gap genes will lead to what?
Loss of body segments
What do pair rule genes control?
Segment polarity genes
Pair rule gene expression is dependent on what?
The interaction of positively and negatively activating transcription regulators
How many stripes are pair rule genes expressed in?
7 stripes
What is the effect of engrailed on wingless?
It cause Wg to be degraded more rapidly = steeper gradient of wingless
What is the phenotype of a wingless mutant?
Lawn of denticles
What is the role of hox genes?
To determine what segment will form along the AP axis
What controls the hox genes?
A combination of gap and pair rule genes
What is meant by a long band germ insect?
All of the 14 segments are defined at once
Give an example of a long band germ insect
Drosophila
What are short/intermediate germ band insects?
Not all of the segments develop at the same time
The head and thoracic segments are made first
Abdominal segments are added on sequentially
Which two genes are crucial for segment addition in Strigamia maritima?
Delta and Notch
Describe the steps on how segments form in Strigimia maritima
ie describe how oscillation occurs
1) The receiving signal (notch) makes repressor (Hes4)
2) Hes4 causes kess activation of the neighbour cell by inhibiting ligand formation (delta)
3) If the neighbouring cell ahs no activation through notch then Hes4 is no longer made
4) The neighbour cell therefore makes more delta and switches on more
