Drosophila body plan

Question 1

Who did the first mutagenesis screens in flies?

Answer 1

Christane Nusslein and Eric Wischaus

Question 2

What is the phenotype in a knirps mutation?

Answer 2

Knirps = little boy in german

They have a shorter middle segment in the larvae

Question 3

What is the phenotype of a gooseberry mutation?

Answer 3

Half of each segment is missing

Question 4

What is the order in which genes are controlled in fly development?

Answer 4

Maternal genes -> Gap genes -> Pair rule genes -> Segment polarity genes

Question 5

What is bicoid?

Answer 5

A DNA binding transcriptional activator
Maternally loaded into the developing oocyte
Has roles in anteriorisation eg in head formation

Question 6

What happens if bicoid is placed in the middle of a bicoid mutant egg?

Answer 6

A mirror image of the thoracic segment will form if bicoid is placed in the middle of the mutant egg

Question 7

Low affinity bicoid binding sites need what to be activated?

Answer 7

High levels of bicoid

Question 8

Where are low affinity bicoid binding sites likely to be found?

Answer 8

In the head structures

Question 9

What is the role of the gap genes?

Answer 9

To control pair rule genes

Question 10

List examples of gap genes?

Answer 10

Hunchback, Giant, Kruppel, Knirps and tailless

Question 11

Mutations in gap genes will lead to what?

Answer 11

Loss of body segments

Question 12

What do pair rule genes control?

Answer 12

Segment polarity genes

Question 13

Pair rule gene expression is dependent on what?

Answer 13

The interaction of positively and negatively activating transcription regulators

Question 14

How many stripes are pair rule genes expressed in?

Answer 14

7 stripes

Question 15

What is the effect of engrailed on wingless?

Answer 15

It cause Wg to be degraded more rapidly = steeper gradient of wingless

Question 16

What is the phenotype of a wingless mutant?

Answer 16

Lawn of denticles

Question 17

What is the role of hox genes?

Answer 17

To determine what segment will form along the AP axis

Question 18

What controls the hox genes?

Answer 18

A combination of gap and pair rule genes

Question 19

What is meant by a long band germ insect?

Answer 19

All of the 14 segments are defined at once

Question 20

Give an example of a long band germ insect

Answer 20

Drosophila

Question 21

What are short/intermediate germ band insects?

Answer 21

Not all of the segments develop at the same time
The head and thoracic segments are made first
Abdominal segments are added on sequentially

Question 22

Which two genes are crucial for segment addition in Strigamia maritima?

Answer 22

Delta and Notch

Question 23

Describe the steps on how segments form in Strigimia maritima
ie describe how oscillation occurs

Answer 23

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