Hedgehog signalling - part 1

Question 1

What does the drosophila hedgehog gene encode?

Answer 1

A secreted protein that functions in many developmental processes

Question 2

What biological processes was the drosophila hedgehog gene originally studied in?

Answer 2

Compartment boundary formation in embryo

Patterning in the wing

Question 3

In some contexts, what does the hedgehog gene induce? And what is this known as?

Answer 3

Induces different responses at different concentrations

Morphogenic action

Question 4

Which organism have most of the details of the hedgehog pathway come from analysis of?

Answer 4

Drosophila

Question 5

What happens when the hedgehog protein binds to patched?

Answer 5

Causes genes to be switched on

Some encode other signalling molecules such as dpp

Question 6

What compartment of the wing disc is hedgehog normally expressed in?

Answer 6

Posterior

Question 7

What technique can you use to get direct expression of hedgehog in the anterior compartment of the wing disc as well as the normal anterior part?

Answer 7

Transgenic tricks such as Gal4-UAS

Question 8

What happens to the wing when there is a direct expression of hedgehog in both the anterior and posterior compartments of the wing disc?

Answer 8

There is a mirror-image duplication of the wing pattern along the anterior-posterior axis

Question 9

What does the vertebrate homologue of hedgehog do?

Answer 9

Also acts in limb patterning

Question 10

Experimentally, how would you look at the function of the vertebrate homologue of the hedgehog gene?

Answer 10

In situ hybridisation using a probe complementary to the mRNA of the chicken sonic hedgehog gene

Question 11

What gene is the vertebrate homologue of hedgehog?

Answer 11

Sonic hedgehog

Question 12

What region of the chick limb bud expresses the sonic hedgehog gene?

Answer 12

Posterior

Question 13

Experimentally, what would you do to look at the consequence of misexpression of sonic hedgehog in the anterior region of the chick limb bud?

Answer 13

Implant a bead soaked with pure sonic hedgehog protein into the anterior region

Question 14

What happens to the chick limb bud if there is a misexpression of sonic hedgehog in the anterior region?

Answer 14

It results in a mirror-image duplication of the chick limb bud

Question 15

What part of the hedgehog and sonic hedgehog genes are homologous?

Answer 15

The molecular pathways but not the structures

Question 16

What sorts of processes does sonic hedgehog act in?

Answer 16

Many developmental processes, e.g.
Primary regulator of cell types in neural tube
Induces feather buds
Kidney development. bone formation

Question 17

What does the vertebrate neural tube do?

Answer 17

Form the brain and spinal cord

Question 18

What is the role of the vertebrate notochord?

Answer 18

Affects development of adjacent neural tube cells by inducing changes in gene expression

Question 19

What is the role of the vertebrate ventral floor plate cells?

Answer 19

Induce differentiation of more dorsal cells

Question 20

What does sonic hedgehog specify in the neural tube?

Answer 20

The ventral portion

Question 21

What does the combination of TFs expressed in the neural tube specify?

Answer 21

The neuronal type

Question 22

What does dpp stand for?

Answer 22

Decapentaplegic

Question 23

What is the role of the zw3 kinase?

Answer 23

Affects eye colouration

Question 24

What are the steps following the induction of a secondary signal by hedgehog?

Answer 24

Hedgehog signalling induces expression of dpp and then dpp diffuses

Question 25

What is caused by the diffusion of dpp?

Answer 25

It induces a pattern along the anterior-posterior axis of the wing

Question 26

Do all cells express dpp?

Answer 26

No, only a band of cells

Question 27

Which is more ancient, the notochord or the neural tube?

Answer 27

The neural tube

Question 28

Do insects have a neural tube?

Answer 28

No

Question 29

When during the life of the vertebrate is the notochord important?

Answer 29

During development, not so much in the adult