Making an Axis

Question 1

Examples of axial patterning

Answer 1

• Frog: sperm entry and organiser graft (DV axis)
• Drosophila: bicoid (AP axis)
• Chick: limb bud SHH (AP axis)

Question 2

Drosophila: organisation of DV axis

Answer 2

Dorsal ectoderm - future epidermis
Neuroectoderm - future nervous system
Mesoderm- future muscle

Question 3

Which gene/s are associated with each region of the blastoderm?

Answer 3

Dorsal ectoderm - dpp
Neuroectoderm - rhomboid
Mesoderm - twist, snail

Question 4

What sets up the dorsal-ventral axis in the Drosophila?

Answer 4

Maternal effect genes

Question 5

3 examples of dorsalised class genes

Answer 5

• Dorsal
• Toll
• Spätzle

Question 6

Example of centralised class gene

Answer 6

• Cactus

Question 7

What are dorsalised class genes required for?

Answer 7

The development of ventral cell fates in the embryo

Question 8

What would happen if the embryo was lacking Toll?

Answer 8

The embryo would become dorsalised ( no ventral structures)

Question 9

Which class of genes are required for the development of dorsal cell fates in the embryo?

Answer 9

Ventralised class

Question 10

What would happen if the embryo was lacking cactus?

Answer 10

Embryo would become centralised (lack dorsal structures)

Question 11

Epistatic analysis of dorsalised and centralised class genes: pathway

Answer 11

Spätzle—> Toll —| Cactus —| Dorsal

Question 12

Spätzle is a ______

Answer 12

Ligand

Question 13

Toll is a ________

Answer 13

Receptor

Question 14

Dorsal is a _________ _______

Answer 14

Transcription factor

Question 15

Cactus binds to ______

Answer 15

Dorsal

Question 16

What is the distribution of Dorsal like in the cytoplasm?

Answer 16

Evenly distributed (unlike bicoid)

Question 17

Toll signalling is active on which side of the embryo?

Answer 17

Ventral

Question 18

Signalling of which protein occurs on the ventral side of the embryo?

Answer 18

Toll

Question 19

What enters on the ventral side of the nuclei?

Answer 19

Dorsal

Question 20

What is the consequence of Dorsal entering on the ventral side of the nuclei?

Answer 20

Creates a concentration gradient of nuclear Dorsal protein due to spätzle only being active on ventral side (activates Toll)

Question 21

What does Dorsal activate?

Answer 21

Transcription of zygotic genes in the mesoderm on the ventral side of the embryo

Question 22

What does Dorsal repress?

Answer 22

Transcription of other zygotic genes so that they are only activated in dorsal regions

Question 23

Which other genes are activated by Dorsal? Do they respond to different thresholds?

Answer 23

Twist, snail, rhomboid. Yes - acts as a morphogen

Question 24

Which gene is repressed by Dorsal?

Answer 24

Dpp

Question 25

In the ventralised mutants what kind of fate do all cells adopt?

Answer 25

Ventral fate

Question 26

In ventralised mutants...

Answer 26

- Dorsal enters whole DV axis - twist, snail, rhomboid activated throughout - dpp expression supressed

Question 27

In the dorsalised mutants what kind of fate do all cells adopt?

Answer 27

Dorsal fate

Question 28

In dorsalised mutants...

Answer 28

- Dorsal protein excluded from nucleus - Mesodermal genes not expressed at all - dpp expressed throughout the embryo

Question 29

Ventralised mutants have no ________ structures

Answer 29

Dorsal

Question 30

Dorsalised mutants have no __________ structures

Answer 30

Ventral

Question 31

Which gene patterns the dorsal side?

Answer 31

dpp

Question 32

dpp forms another ________ gradient

Answer 32

Morphogen

Question 33

During gastrulation, what moves inside the embryo?

Answer 33

The mesoderm

Question 34

What does the mesoderm moving inside the embryo during gastrulation give rise to?

Answer 34

Muscles of the larva

Question 35

After gastrulation, what is now on the ventral side?

Answer 35

Neuroectoderm

Question 36

After gastrulation, the neuroectoderm is now on which side?

Answer 36

Ventral side

Question 37

Role of the Toll pathway in the innate immune response

Answer 37

Stimulated by bacterial and fungal infection in adult flites

Question 38

In vertebrates, where are Toll-like receptors expressed?

Answer 38

Macrophages