DV axis formation in drosophila

Question 1

What are the 2 major classes of DV mutant?

Answer 1

1. Maternal

2. Zygotic

Question 2

What is a maternal mutant?

Answer 2

When the mother’s genotype produces a mutant offspring.

Question 3

What is dorsal?

Answer 3

A DV morphogen.

Question 4

Where is a) dorsal protein and b) dorsal mRNA found in the embryo?

Answer 4

a) Localised ventrally

b) Uniformly distributed in the cytoplasm

Question 5

Why is dorsal different from the other morphogens studied?

Answer 5

Usually mRNA and protein are found together.

Question 6

What is torpedo?

Answer 6

A transmembrane receptor expressed in follicle cells.

Question 7

What is Gurken?

Answer 7

A secreted protein expressed by the oocyte.

Question 8

Where is gurken found in the oocyte?

Answer 8

Clustered around the nucleus.

Question 9

What happens when gurken binds torpedo?

Answer 9

The microtubules become polarised and extend along the AP axis.

Question 10

What happens once the microtubules have elongated?

Answer 10

A symmetry breaking event: the nucleus migrates anteriorly.

Question 11

What does gurken cause the follicle cells to do?

Answer 11

Dorsalise.

Question 12

What gene does gurken-torpedo binding inhibit?

Answer 12

Pipe.

Question 13

Where is pipe inactivated?

Answer 13

On the dorsal side in the follicle cells, but active on the ventral side.

Question 14

Pipe initiates a signalling cascade that ends in what?

Answer 14

The degradation of cactus.

Question 15

What does the degradation of cactus lead to?

Answer 15

Dorsal being released into the nucleus.

Question 16

Thus the whole point of gurken-torpedo signalling is?

Answer 16

To cause symmetry breaking and cause the release of dorsal into the nucleus.

Question 17

What is the amnioserosa?

Answer 17

Part of the embryonic membrane

Question 18

What is the neurogenic ectoderm?

Answer 18

Where the neuroblasts delaminate from.

Question 19

How many types of neuroblast originate from the neurogenic ectoderm?

Answer 19

3.

Question 20

What does the degradation of cactus lead to?

Answer 20

Dorsal being released into the nucleus on the ventral side of the emrbyo.

Question 21

Thus the whole point of gurken-torpedo signalling is?

Answer 21

To cause symmetry breaking and cause the release of dorsal into the nucleus on the ventral side.

Question 22

Which 3 genes does dorsal, after it enters the nuclei on the ventral side of the embryo, activate? What do they have in common?

Answer 22

1. snail
2. twist
3. rhomboid

They are all ventral determinants.

Question 23

Which 3 genes does dorsal inhibit on the ventral side of the embryo? What do they have in common?

Answer 23

1. decapentaplegic
2. tolloid
3. zerknullt

They are all dorsal determinants.

Question 24

What are the 2 major classes of DV mutant?

Answer 24

1. Maternal

2. Zygotic

Question 25

Of snail, twist and rhomboid, which has the broadest domain within the blastula and why?

Answer 25

Rhomboid: it is activated by intermediate levels of dorsal.

Question 26

What is sog?

Answer 26

A ventral morphogen that acts later in development.

Question 27

Where is sog located?

Answer 27

In the neurogenic ectoderm.

Question 28

What does sog inhibit and why?

Answer 28

Sog inhibits ventral-ward diffusion of Dpp to maintain the boundary.

Question 29

Which gene degrades sog?

Answer 29

Tolloid.

Question 30

What does the interaction between sog and Dpp/tolloid do?

Answer 30

Generates gradients that help neurogenic ectoderm differentiate into nerve cells.

Question 31

What is Dpp?

Answer 31

A later-acting dorsal morphogen.

Question 32

What is twist?

Answer 32

A TSF that regulates mesoderm formation.

Question 33

What is a zygotic mutant?

Answer 33

Where the zygotic genome is responsible for mutation.

Question 34

What is characteristic about zygotic mutants?

Answer 34

They are usually eithr completely dorsalised or completely ventralised.

Question 35

What has comparative anatomy revealed about the DV axis in a) invertebrates and b) vertebrates?

Answer 35

a) The nerve cord is ventral and the heart is dorsal | b) The heart is ventral and the nerve cord is dorsal

Question 36

In invertebrates, Dpp is a dorsal determinant: a) What is Dpp's homologue in mice? b) Where is it located?

Answer 36

a) Bmp4 | b) Ventrally

Question 37

What do invertebrate Dpp and vertebrate Bmp4 both do?

Answer 37

Are involved in the formation of tissues like the heart, blood, eye etc.

Question 38

In invertebrates, sog is a ventral determinant: a) What is sog's homologue in mice? b) Where is it located?

Answer 38

a) Chordin | b) Dorsally

Question 39

What do invertebrate sog and vertebrate chordin both do?

Answer 39

Specify regions of the CNS in the same order.

Question 40

What happens if you interchange sog and chordin in experiments?

Answer 40

They do exactly the same thing.

Question 41

Define innate immunity.

Answer 41

General immune response that involves the production of non-specific peptides. Insects only have this immunity.

Question 42

The mammalian immunity genes of NF-kappaB and its repressor kappaB are homologous to which invertebrate genes? What do these genes do?

Answer 42

Dorsal and cactus: although they are DV genes they also involved in insect innate immunity.