DV axis formation in drosophila Flashcards
What are the 2 major classes of DV mutant?
- Maternal
2. Zygotic
What is a maternal mutant?
When the mother’s genotype produces a mutant offspring.
What is dorsal?
A DV morphogen.
Where is a) dorsal protein and b) dorsal mRNA found in the embryo?
a) Localised ventrally
b) Uniformly distributed in the cytoplasm
Why is dorsal different from the other morphogens studied?
Usually mRNA and protein are found together.
What is torpedo?
A transmembrane receptor expressed in follicle cells.
What is Gurken?
A secreted protein expressed by the oocyte.
Where is gurken found in the oocyte?
Clustered around the nucleus.
What happens when gurken binds torpedo?
The microtubules become polarised and extend along the AP axis.
What happens once the microtubules have elongated?
A symmetry breaking event: the nucleus migrates anteriorly.
What does gurken cause the follicle cells to do?
Dorsalise.
What gene does gurken-torpedo binding inhibit?
Pipe.
Where is pipe inactivated?
On the dorsal side in the follicle cells, but active on the ventral side.
Pipe initiates a signalling cascade that ends in what?
The degradation of cactus.
What does the degradation of cactus lead to?
Dorsal being released into the nucleus.
Thus the whole point of gurken-torpedo signalling is?
To cause symmetry breaking and cause the release of dorsal into the nucleus.
What is the amnioserosa?
Part of the embryonic membrane
What is the neurogenic ectoderm?
Where the neuroblasts delaminate from.
How many types of neuroblast originate from the neurogenic ectoderm?
3.
What does the degradation of cactus lead to?
Dorsal being released into the nucleus on the ventral side of the emrbyo.
Thus the whole point of gurken-torpedo signalling is?
To cause symmetry breaking and cause the release of dorsal into the nucleus on the ventral side.
Which 3 genes does dorsal, after it enters the nuclei on the ventral side of the embryo, activate? What do they have in common?
- snail
- twist
- rhomboid
They are all ventral determinants.
Which 3 genes does dorsal inhibit on the ventral side of the embryo? What do they have in common?
- decapentaplegic
- tolloid
- zerknullt
They are all dorsal determinants.
What are the 2 major classes of DV mutant?
- Maternal
2. Zygotic
Of snail, twist and rhomboid, which has the broadest domain within the blastula and why?
Rhomboid: it is activated by intermediate levels of dorsal.
What is sog?
A ventral morphogen that acts later in development.
Where is sog located?
In the neurogenic ectoderm.
What does sog inhibit and why?
Sog inhibits ventral-ward diffusion of Dpp to maintain the boundary.
Which gene degrades sog?
Tolloid.
What does the interaction between sog and Dpp/tolloid do?
Generates gradients that help neurogenic ectoderm differentiate into nerve cells.
What is Dpp?
A later-acting dorsal morphogen.
What is twist?
A TSF that regulates mesoderm formation.
What is a zygotic mutant?
Where the zygotic genome is responsible for mutation.
What is characteristic about zygotic mutants?
They are usually eithr completely dorsalised or completely ventralised.
What has comparative anatomy revealed about the DV axis in a) invertebrates and b) vertebrates?
a) The nerve cord is ventral and the heart is dorsal
b) The heart is ventral and the nerve cord is dorsal
In invertebrates, Dpp is a dorsal determinant:
a) What is Dpp’s homologue in mice?
b) Where is it located?
a) Bmp4
b) Ventrally
What do invertebrate Dpp and vertebrate Bmp4 both do?
Are involved in the formation of tissues like the heart, blood, eye etc.
In invertebrates, sog is a ventral determinant:
a) What is sog’s homologue in mice?
b) Where is it located?
a) Chordin
b) Dorsally
What do invertebrate sog and vertebrate chordin both do?
Specify regions of the CNS in the same order.
What happens if you interchange sog and chordin in experiments?
They do exactly the same thing.
Define innate immunity.
General immune response that involves the production of non-specific peptides. Insects only have this immunity.
The mammalian immunity genes of NF-kappaB and its repressor kappaB are homologous to which invertebrate genes? What do these genes do?
Dorsal and cactus: although they are DV genes they also involved in insect innate immunity.
