History/Basic Concept & Drosophila development Flashcards
Specification State
Received instructions, but doesn’t have to follow, can still be influenced by the environment where it can change its fate if the environment changes (really more on potential than fate so it’s less committed)
Determination State
Received instructions but can’t change fate has to follow instructions. It also can’t be influenced by environment so potential & fate are equal therefore its more committed
Testing Specification
They removed a cell from its embryo (an eye cell) & grew it in a neutral media with no new stimulus, when they put the eye cell into a neutral media it was not specified if it didn’t receive signals to become an eye & express eye gene (blastula)
When testing specification what resulted if the eye cell was specified?
If it was specified it received signal to become an eye & express eye gene (gastrula)
Testing determination
They put an eye cell in a non-neutral environment so that it does have different stimulus & also challenge the cell in different environments
What happened when testing the determination when the cell is not determined?
If the cell is not determined, then its influence by the environment where if you put an eye cell into muscle environment it becomes a muscle (gastrula)
What happened when testing the determination when the cell is determined?
If the cell is determined, then it’s not influenced by the environment where if your put an eye cell (Or neurula) into a muscle environment it still stays as an eye cell
Development Commitment
- Specification (less committed) (blastula to gastrula)
- Determination (more committed) (gastrula to neurula)
- differentiation (neurula to embryo)
Induction
Is cell to cell signaling, where one cell induces another
What are the different inductive interactions??
- Diffsuion
- Direct Contact
- Gap Junction
Diffusion
An induction interaction where one cell has a receptor
Direct Contact
An inductive interaction where both cells have receptors
Gap Junction
An inductive interaction where both cells are connected together
The inducer in an inductive interaction
Makes the signal in an inductive interaction
The responder in an inductive interaction
In an inductive interaction the responder gets induced only if its competent (has a receptor or signaling pathway)
How can a cell lose its competence over time?
By differential gene expression
Morphogen
Molecule secreted by an inducer (specifies by concentration gradient & cells respond to different concentration)
Asymmetrical division
Leads to cell differentation
Fly development is similar to human development where it __________
Conserves Genes
Describe a fly development
- Develop inside eggs
- Larva Hatch
- Pupa
- Metamorphosis to an adult
Pole cells (common strategy to allocate germ cells early)
- Posterior
- Outside of blastoderm
- Pole cell turn into gametes germ cells
- Blastoderm turn into somatic cells
Gastrulation
Occurs after cellularization & makes 3 germ layers
What are the 3 germ layers that gastrulation makes?
- Ectoderm (outside)- found in the cuticle & nervous system
- Mesoderm (middle)- found in muscle, heart, & blood
- Endoderm (Inside)- found in gut
The germ layers is the ________
Unit of lineage
Gastrulation is also the _________ in the ventral region
Invagination (Endoderm & mesoderm move inside & ectoderm cover the outside)
Segmentation
Occurs after gastrulation
Larva Hatches (24hpf) (For drosophila)
- They grow without any wings or legs & have imaginal disk (primordial stem cells
- Molts 2x & they become pupa
Pupa goes through ___________ to become an adult
Metamorphosis (They change their form & the imaginal disk becomes organs)
Nüsslein-Volhard + Wieschaus
Did a large-scale mutagenesis on drosophila & found out that random mutagenesis leads to random mutant
What did Nüsslein-Volhard + Wieschaus find in their studies?
That the gap genes makes segments
What is the axis of formation for syncytium?
- A-P (Anterior -posterior)
2. D-V (Dorso- Ventral)
A-P axis
Has 3 regions
D-V axis
Has 4 regions
A-P & D-V axis
Organized simultaneously & have different mechanisms
What are the maternal factors set up axes?
- RNAs, proteins in the egg (occurs before fertilization & is predetermined)
- Usually RTFs- regulate early development & activate zygotic genome
- Zygotic genome- from a diploid nucleus & expressed after feralization
What are the two classes of maternal genes for A-P axis for drosophila?
- Bicoid anterior formation (mutant with no head)
2. nanos posterior formation (mutant with no abdomen)
________ is necessary for anterior structures
Bicoid
- RTF
- mRNA anterior of egg
- Translation occurs after fertilization
- A-P gradient increases the anterior
- 1st morphogen gradient discover
__________ expression of eye gene sufficient to make eyes elsewhere
Ectopic
_______ is necessary for posterior structures
nanos
- mRNA posterior of the egg
- Translation occurs after fertilization (protein diffuses)
- A-P gradient increases posterior
- Not RTFs - works indirectly & translation of maternal hunchback mRNA in posterior
Hunchback
- Needed for anterior development & shouldn’t be present in posterior
- Nanos suppresses posterior hunchback translation (creates hunchback gradient)
- Wont form anterior structures in posterior region
Maternal genes for D-V axis
- Dorsal protein- uniform distribution (cytoplasmic)
- Toll receptor (inactive) - uniform distribution on the surface, gets activated in ventral
- Toll receptor activated only in ventral
- Dorsal enters ventral nuclei (gets D-V gradient)
When toll is inactivated
Cactus keeps Dorsal in cytoplasm
When toll is activated by ligand
- it activates Cactus kinase (phosphorylates Cactus)
- P-Cactus is degraded
- Dorsal enters nucleus (turns on genes)