Development L3/4 Flashcards
What are maternal effect mutations? (draw diagram)
Mutations have effect only when present in mother and none if present in father
What did screening for maternal-effect mutations in drosophila reveal?
Genes encode products required for normal structure development a) along atero-prosterior axis b) in germ cell formation c) in dorso-ventral axis d) in embryo terminii
How can antero-prosterior maternal effects be classed?
(see notes for diagram) –> bicoid, nanos, torso
How can bicoid phenotype be rescued and how can you make head structures form in middle of embryo?
add WT anterior cytoplasm to bicoid mutant egg in diff places
Draw bicoid maternal transcript and bicoid protein gradient
(see notes for diagram)
How are bicoid and oskar made to segregate?
Transported along microtubules, specificity depends on 3’ UTR, bicoid moves with dynein to negative end (anterior), oskar moves with kinesin to positive end (prosterior)
What happens if Oskar transcript fitted with bicoid 3’UTR?
Oskar mRNA move with bicoid RNA to anterior (-ve end) via dynein
Why do cells move RNA and not protein itself?
1) Easier bc smaller 2) prevents protein function before it gets to the right place 3) can make a more localised higher conc –> all translated in one position allowing complexes that need high conc to form
What is fucus and how does it put its axes in?
(see notes for diagram)
How does Xenopus put its axes in?
(see notes for diagram)
What does VegT code for and how does it and Wnt11 move?
VegT : codes for TF for growth factor, associates with yolk at vegetal pole
Wnt11: closer to the plasma membrane in the cortical cytoplasm, rotates by 30 degrees when sperm fertilises
What do animal and vegetal parts of the embryo exclusively form if cultured separately?
Animal : ectodermal
Vegetal: endodermal
When are mesodermal cell types formed?
When 2 halves of embryo come into contact
What do vegetal cells do to help form mesoderm?
They are a source of signal telling animal cells to make mesoderm
What is gastrulation?
When a 3d embryo forms from a 2d cell sheet, at the end the blastocoel (fluid-filled cavity in middle) is gone and embryo is surrounded by ectoderm, endoderm is internalised and mesoderm is between the 2
(epiboly = process of ectoderm moving round)
What was the nobel-prize winning experiment designed to make embryos heterzygous for mutants that disrupt body patterning?
(see notes for diagram)
What is used in drosophila to look at patterns?
The regular pattern of hooks (denticles)
Dentricles are the feet of larvae allowing them to grip and move through food source
What are 3 main types of drosophila genes that dirupt early embryo patterning?
Gap gene, determines pair rule genes, determine segment polarity genes
What is the hedgehog gene and why was it named this?
In mutant it produced dead embryo with prickly dentricle pattern
Encodes diffusible signalling molecule important for segment patterning, also found in vertebrates, termed sonic hedgehog(they already had 1 hedgehog gene :) )
Used for CNS and limb development
What is the french flag model?
(see notes for diagram)
How positional values are interpreted depends on genetic instructions active in cell group and is influenced by their developmental history
Cells from one group transplanted to another read their new position and differentiate accordingly but following previously assigned program
What is the proximo-distal sequence of chicken limb?
Humerus –> ulnar/radius –> wrist –> digits
What is the antero-prostero sequence of digits?
2 –> 3 –> 4
What happens when hind limb cells are transplanted into a fore limb bud?
They differentiate according to their position in the limb bud but make hind limb structures
Draw diagram explaining progress zone
(see notes for diagram)
