Morphogenesis (cleavage and gastrulation) in drosophila I Flashcards
What happens after fertilisation of the oocyte nucleus?
Series of v rapid nuclear divisions
How do the rapid nuclear divisions occur?
In the absence of any cell division
What happens to the nuclei in the oocyte after nuclear divisions?
They migrate out to the surface and form a syncytial blastoderm
What happens after syncytial blastoderm formation?
Membranes grow down between each individual nucleus to isolate them and form a cell
Cellular bastoderm stage?
Membranes growing down between the nuclei in the syncytial blastoderm, forming many individual cell
What structure does the cellular blastoderm have?
Epithelial sheet, folded into an egg shape
Which axes are cells specified along?
Anterior posterior and dorsal ventral
What is positional information?
A cell knowing where it is in the organism
What is spatial specification reflected in?
The expression of diff genes
When observing genes, what do stripes along a body axis show?
They correspond to the eventual body segments
What does the egg contain when it is laid (that helps spatial specification)?
Molecules which are going gradients of morphogens–> specify position along both axes
Where is bicoid mRNA localised to?
Anterior pole of the egg
When is the bicoid gene espressed?
Oogenesis
What does the bicoid RNA serve as a source of?
bicoid protein
What does bicoid encode?
A TF
What does bicoid mRNA act as when it localised to the anterior egg pole?
The source of a gradient of Bcd protein
Result of embryos having a mutated bicoid gene?
lack anterior structures–>mos anterior structure is replaced by most posterior structre
What is bicoid involved in (w/ other maternal factors expressed in the posterior end)?
Control the expression of the first set of genes to be expressed by the zygote
What are GAP genes?
the first set of genes to be expressed by the zygote
What happens following the expression of GAP genes?
The embryo becomes subdivided into repeating units
What are the repeating units that the embryo has?
The precursors to the body segments which will differentiate at the end of embryogenesis
What are pair rule genes?
expressed in alternating domains along the body axis
How is the spatially restricted expression of pair-rule genes ?
By combinatorial activity of Gap gene proteins
Where is dorsal distributed?
In a gradient along the dorso-ventral axis
