Developmental genetics - lecture 3 last series Flashcards
What is superficial cleavage in drosophila zygotes?
Rapid nuclear divisions without forming separate cells.
What are pole cells and how are they formed?
Cells at the posterior end hat will go on to form the germ cells. They are formed when nuclei move to the posterior end.
What is the main feature of a syncytial blastoderm?
When the remaining nuclei move to the outer edges.
What is the main feature of a cellular blastoderm?
Cell membranes have formed around all of the cells.
Are there nuclear/cell divisons in gastrulation?
No lol.
What happens regarding the head region in gastrulation?
A head regions forms at the anterior end - demarked by the cephalic fold. A ventral furrow appears on the ventral surface and cellular movements begin to occur.
What happens regarding future mesodermal cells in gastrulation in drosophila?
The future cells are moved into the embryo by invagination - this tube of mesodermal cells then dissociates to form a layer internally.
What is germ-band extension?
The movement of ventral tissue around the posterior end and onto the dorsal side. Cells of the future anterior and posterior midgut invaginate into the embryo and eventually fuse to form the gut.
What is the result of germ-band extension?
It means that the posterior cells are at the dorsal side - they are curled over and will straighten out and the posterior end will be where the anus forms.
How does neurulation differ from frogs and mammals?
In frogs and mammals there is a tube that forms the nervous system but this is not the case for drosophila. The neuroblast embryo forms the cells that forms the nervous system and there is no spinal cord.
What are halteres?
Balancing organs so the drosophila can fly.
What is a genetic screen?
A technique used to identify and study an interesting phenotype within a mutated population.
What are the three key steps in genetic screening?
- Generate the mutants 2. Identify the genes that are mutated. 3. Find where the genes are expressed.
How can the mutants be generated for a genetic screen?
Males can be mutagensised. They are left to breed. As the mutation often leeds to a recessive phenotype it can be hard to tell which offspring have the mutated gene. The offspring can then be bred with a wild-type partner to form the F2 generation. The F2 generation are then inbred and it is not possible to see which offspring contain a mutated gene.
Why are drosophila well suited to genetic screens?
They have a quick generation time, a simple genome, they are small and cheap to maintain and it is easy to see the phenotype.
