Invert dev - new Flashcards
1
Q
Describe complementation analysis and when it might be used.
A
- When used: To see if two seperate mutant organisms with same phenotype have mutation on same gene.
Process:
- cross mutant A with mutant B
- If offspring are wild-type:
- mutations of different genes –> complementary
- If offspring are mutant phenotype:
- mutations on same gene –> not complementary
2
Q
Explain the difference between regulative and mosaic development
A
- Regulative development:
- Cell will develop according to signals from cells surrounding it, is not fated to become a specific type of cell.
- Mosaic development:
- Cell is fated to become a specific cell type. C. elegans is like this
3
Q
How does sperm promote posterior cell fate in C. elegans?
A
The sperm provides the polarity cue, causing the polarization of PAR-2 and PAR-3.
4
Q
- What are SynMuv genes?
- Where are they located?
- How many classes of them exist and why is this important?
- What is their function in terms of VPCs?
- How do they mostly regulate?
A
-
What are SynMuv genes?
- Synthetic Multivulval genes
-
Where are they located?
- located in Hyp7 epidermis rather than VPCs
-
How many classes of them exist and why is this important?
- Class A and B
- Are functionally redundent, so both have to be mutated to have an effect
-
What is their function in terms of VPCs?
- prevent inappropriate lin-3 expression in the hyp7
-
How do they mostly regulate?
- are epigenetic regulators controlling transcription
5
Q
What role does lateral inhibition play in VPC patterning?
A
- Inductive signal tells P5.p, P6.p and P7.p to become 1 and 2 cells.
- Is strongest with P6.p, so it becomes 1 cell first
- 1 cells send out signal telling cells next to them not to become 2 cells
6
Q
What is lin-12 and what happens in case of a lin-12(lf) mutation?
A
- Encodes a notch-like receptor important in lateral inhibition
- In case of lin-12(lf), all 1 and 2 VPCs will become 1 VPCs
7
Q
List the 5 vulval development steps
A
- generation of VPCs
- Vulval precursor patterning
- generation of adult cells
- Anchor cell invasion
- Morphogenesis of vulva
8
Q
Describe the basic role of PAR proteins
A
- Ensure taht first embryonic division is asymmetric
- Can regulate localization patterns of each other
- Activities of Par proteins ensure asymmetric partitioning of P-granules and cell fate determinants like SKN-1
9
Q
Role of PIE-1
A
- essential regulator of germ cell fates
- can inhibit mRNA transcription to block somatic development
- prevents P2 from becoming EMS
- encodes CCCH zinc finger protein that is partitioned into P1, P2, P3, P4
- Is required for expression of NOS-2 which promotes primordial germ development
- PIE-1 remaining in anterior blastomere is degraded, requiring ZIF-1
10
Q
Role of ZIF-1
A
- Is SOCS-box protein
- interacts with different proteins that are required for CCCH finger protein degredation
- Segregation of germ plasm involves both stabilization of germline proteins in germ line and cullin-dependent degredation in the soma
11
Q
Describe function of Mex5/6
A
- Function to establish Soma/Germline asymmetry in early C. elegans embryos
- Regulate cell fate by regulating mRNA translation, incluidng zif-1 mRNA
- localiztion regultated by PAR-1
- diffuses faster in posterior (doesn’t stay as long)
- likely that Mex-5 function is to inhibit anterior expression of germline proteins
12
Q
Describe the role of Wnt signaling in C. elegans embryonic development
A
- Wnt ligand binds LRP and Frizzled to start signaling pathway
- Lit-1(ts) permits wide scale blockage of Wnt signaling
- Wnt signaling polarizes an early C. elegans blastomere to distinguish endoderm from mesoderm
- Regulates orientation of cell division
- a posterior center establishes and maintains polarity of C. elegans embryo by Wnt-dependent signaling
- posterior cells assumer anterior fates when Wnt signaling is blocked
13
Q
Give a brief description of heterochronics and heterochrony
what are Alae?
A
- Heterochrony: developmental change in timing or rate of events, leading to changes in size and shape
- Alae: adult specific ridges in cuticle on worm (is a way to say that it is an adult)
- A hierarchy of genes control larva to adult development in C. elegans
14
Q
Describe role of Lin-14 and 2 types of mutations
A
- Role: works in early stages of development to inhibit lin-29 and stop if from flipping switch to go from larval to adult form
mutations:
- Retarded: semidominant mutant, is seen in T-lineage
- in L2 stage, T.ap generates a cell division pattern and ascendent cell types similar to those normally generated during L1 by T cell.
- Precocious: in recessive lin-14 mutant
- T cell precociously generates cell division pattern normally generated during L2 by T.ap
15
Q
Function of lin-4 and how it works
A
- Encodes small RNAs with antisense complimentarity to 3’ UTR of lin-14
- inhibits lin-14 translation
- Mediates temporal pattern formation in C. elegans by creating temporal gradient in lin-14
16
Q
Describe role and method of let-7
A
- regulates temporal timing in C. elegans
- transition from late larva to adult requires let-7 RNA
- binds to 3’UTRs of target mRNAs
17
Q
Describe role of daf-12
A
- Encodes a nuclear receptor that regulates the dauer diapause and development age in C. elegans
- when daf-12 is active, it inhibits activity of let-7, allowing larva to go to adult form
18
Q
Describe transposable elements and how they are evolutionarily useful.
A
- are mobile genetic elements that are moved from one position in the genome to another
- each carries unique set of genes
- catalyzed by transposases
- useful because induce genetic variance
- diagram depicts “cut and paste” transposition
19
Q
How can GFP be useful in fly genetics
A
Can be inserted into genome to trace cells in space and time
20
Q
Name some ways in which flies may be messed with
A
- Can possibly kill specific cells and see what happens
- Can interfere with gene function in specific cells (RNAi, over expression)
- Can induce recombination during mitosis in specific cells (generation of a clone)
- Can block or force electrical activity (neurons)
- Induced by shining light at right wavelength at different neurons and can induce electrical activity
21
Q
Describe an enhancer trap and what it may be used for
A
- Timing of gene expression is controlled via small pieces of DNA called enhancers which help control gene expression patterns
- can insert DNA into fly genome with weak promotor and reporter gene
- DNA will only be activated if enhancer activates, telling you when and where that enhancer becomes activated.
22
Q
Describe Uas/Gal4 system
A
- A tissue specific enhancer triggers the expression of the Gal4 transcriptional activator
- Gal4 can be regulated by any chosen promotor
- Gal4 binds to UAS enhancer sequences
- DNA downstream of the UAS sequence will then only be expressed when Gal4 is expressed.
- Can thus use this system to turn genes on and off
- Can mate a fly line with the Gal4 with a fly line containing UAS connected to a different gene, rather than creating a new fly each time
23
Q
Descripe Gap genes
A
-
Gap: Blocks of segments are missing
- Mutation results in loss of contiguous body segment, resulting in fly missing that part
24
Q
Describe pair rule genes
A
-
Pair rule: even or odd segments are missing
- Result of differing concentration of Gap gene proteins
- Defined by effect of mutation that causes loss of normal development patter in alternating segments
25
Describe segment polarity genes
* **Segment polarity:** denticle are duplicated in a mirror image
* Hedgehog, Wnt signaling
* Mutation leads to segments not being properly separated
26
What are Cis-regulatory elements?
* **Cis-regulatory elements**:
* Regions of non-coding DNA that regulate the transcription of neighboring genes
* Contain multiple binding sites for various factors (transcription factors)
27
How is patterning information coded in cis-regulatory elements?
* A morphogen activates expression of target genes
* Target gene activation and therefore the patterning output depends on:
* Morphogen concentration
* Binding site affinity in target genes
28
Describe Bicoid mutants
* ***Bicoid* mutants:** form posterior structures instead of a head, and lose anterior segments
* Phenotype found in embryos where mother is homozygous for *bicoid*. *Bicoid* gene must be provided maternally
29
What are the different types of genes needed for embryonic development and a good analogy for them?
* “realisator” genes (“workers”)
* “selector or architect” genes (“architects”) that coordinate and regulate the realisator
30
Define an imaginal disc
* Proginator tissue in larvae from which adult tissues develop
* Example: wing imaginal disc corresponds to a developing hemi-thorax and a wing
31
Give a brief summary of the stepwise process in terms of gene progression (imaginal disc to adult structure)
* **Prepattern**
* Regional expression of patterning genes
* Establishment of a pre-pattern of cell territories
* **Acquisition of neuronal competence**
* Expression of proneural genes in small groups of cells
* **Singling out a neural precursor**
* Mutual inhibition among proneural cells
* Emergence of a precursor
* **Lateral inhibition**
* Neuronal precursor inhibit remaining cells of the proneural group
* Proneural cells return to epidermal fate
* **Fixed neuronal lineage**
* Fixed number of divisions
* Asymmetrical segregation of fate determinants
* **Differentiation**
* Sister cells assume their final shape and acquire their properties
* Neurons grow neurites and establish their final connectivity
32
describe step 1 of the notum development
* **_Step 1: defining a large region where sense organs will develop_**
* Prepatterning genes
* e.g. - Iroquois
More info:
* *iroquois* complex defines top domain
* Other genes define the central domains: *pannier, u-shaped*
* These genes are called **pre-patterning** genes; they are transcription factors and are expressed very early during thorax development
33
describe step 2 of the notum development
* **_Step 2: defining smaller regions of neural competence_**
* Proneural genes
* e.g. achaete, scute
More info:
* Small groups of epidermal cells (~30-40) acquire the transient competence to become a sensory organ precursor
* This competence is give to the so-called **proneural genes**, and it later restricted to a single precursor per group, the **sensory organ precursor (SOP)**
* For the bristles, the proneural genes are the transcription factors ***achaete*** and ***scute***
* Other proneural genes determine the formation of other sense organs (e.g. ***atonal, amos)***
* Proneural genes and their function are generall conserved in vertibrates
* From prepattern to proneural genes
* The patchy expression of ***achaete*** and ***scute*** is determined by an array of regulatory elements responding to iroquois
34
describe step 3 of the notum development process
* **_Step 3: singling out a sensory precursor cell_**
* Mutual inhibition - Notch/Delta cell-cell interactions
* SOP (sensory organ precursor) defined here
More info:
* The emergence of a single precursor among the proneural group results from competition among the cells in this group.
* This competition, called **mutual inhibition** happens through cell-cell interactions mediated by the receptor **Notch (N)** and the ligand **Delta (DI)**
* When the competition does not happen (mutants), all proneural cells become sensory precursors
* **Notch, Delta** and the entire signaling pathway they trigger constitute the **neurogenic** genes, which restrict the development of proneural cells into **SOPs**
* The Notch/Delta system
* **Notch (N)** and **Delta (DI)** are transmembrane receptors expressed at the cell surface.
* Upon binding by **DI**, **Notch** undergoes cleavage of its intracellular domain **(ICE)** which triggers a signaling pathway
* The output of the signaling pathway downstream of **N** is the repression of the neural fate.
* ***DI*** expression is promoted by **Scute**
* A cell that expressed more **Delta** may win the competition
* The proneural group may transition from a situation where all the cells maintain each other in a repressed state, to a situation where one cell expressing more **DI** represses its neighbors and becomes the **SOP**
35
describe step 4 of the notum development process
* **_Step 4: Lineage control and asymmetric divisions_**
* SOP (sensory organ precursor) divides
* Has a fixed lineage
More info:
* A freshly selected **SOP** starts to divide. The pattern and number of divisions is constant for a given type of sensory organ. This is a **_Fixed lineage_**
* The lineage generates a **bristle**, **a socket, a glial cell** and one or more neurons
* At each step of the lineage, cellular decisions are made
* Any mistake leads to an aberrant sensory organ
* Decision-making in the sensory lineages
* Asymmetric segregation of specific proteins result in distinct daughter cells
* Recycling Notch and Delta to choose cell fate during the lineage
* The daughter cells of the second division of the **SOP** lineage “fight” to choose their fates
The fight is biased by the asymmetric segregation of a cytoplasmic determinant
36
describe step 5 of the notum development process
* **_Step 5: an aspect of differentiation, establishing the correct neuronal connections_**
* sensory neurons extend an axon to VNC
* Neurons start connecting to each other
* this step is an aspect of differentiation
More info:
* Sensory neurons of the thorax extend an axon to the ventral chord **VNC**, the posterior part of the central nervous system
* In the **VNC**, each neuron extends 2 branches along the antero-posterior axis
* The shape and position of these projections vary with the organ.
* The ultimate aspect of sense organ differentiation is controlled by the earliest gene in the cascade
* Although the proneural genes ***achaete*** and ***scute*** give an information on the type of sense organ, interfering with their function does not affect the projection
* In contrast, the function of ***Iroquois*** is necessary and sufficient to determine where and how the neuron projects to the brain.
37
Which genes are important in development of wing primordium?
* This wing identity results in wing cells expressing the genes ***vestigial*** and **scalloped**
* The **wing primordium** is determined by the intersection of ***dpp*** and ***wg*** expression
38
To which segments is the wing primordium restricted, and how?
T2 and T3 by HOX genes
39
Purpose of clonal analysis
* Mark cells at defined developmental times and see where they end up in the adult wing
* Cells can be marked genetically by making them homozygous for a recessive mutation as they grow.
40
How can cells be modified to grow faster in clonal analysis and why does this help?
* A growth advantage can be conferred to the cells of the clone by exploiting the mutation **Minute**
* **Minute:** a mutation modifying a genetic factor involved in rate of development
* This gives big clones, but also reveals rules of cell growth.
41
how is compartmental identity defined?
* The compartmental identity is defined by expression of the **selector genes**
* **Engrailed:** Posterior
* **Apterous:** dorsal
42
What does Dpp do?
* **Dpp** is a morphogen that signals at short and long distance
* Once the AP boundary exists, ***dpp*** is produced there and diffuses, creating a symmetrical gradient
* The ***dpp*** gradient is read by target genes responding to different concentrations, thereby creating different domains in the wing.
43
How can a cell undergo mitosis and at the same time retain a stem cell state?
* A **microenvironment** facilitating self-renewal or **asymmetrical distribution of cell fate determinants** (or both)
* Microenvironment: **stem cell niche** created by support cells
* Allows to maintain proliferative potential of stem cells and allows differentiation.
44
4 steps in the life cycle of a germ cell and the processes that affect germ cell formation and maintenance
* Germ cells first have to be **specified** = Primordial Germ Cells (**PGC**s)
* PGCs **Migrate** to find the **SOMATIC GONAD**
* In the **niche** PGCs adopt **sexual identity** and form a stem cell population **= Germline Stem Cells (GSC)**
* Germ cells initiate **meiosis** and form gametes
45
What is the function of germ plasm?
* Primordial germ cells are specified by the **GERM PLASM**
* The function of the **Germ Plasm** is to prevent differentiation of progenitors of germ cells into somatic tissues
* Nuclei which end up in the Germ plasm will become PGCs
46
* Name 5 **maternal mRNAs** localized to the germ plasm and necessary for germ cell formation (8 total, 5 important ones to remember)
* ***Oskar***
* ***Nanos***
* ***Vasa (conserved germ cell marker)***
* ***Pole granule component (pgc)***
* ***Trapped in endoderm-1 (tre-1)***
* *Tudor*
* *Pumilo*
* *Germ cell less (gcl)*
47
What is the role of Oskar in germ plasm formation?
* Localizing ***oskar*** at the anterior pole is sufficient to induce germ plasm and ectopic PGC formation:
* **Oskar** is the only sufficient factor
* Role of ***oskar*** in germ plasm formation: has a central, duel role.
* As an RNA-binding protein it crosslinking to **nanos, pgc,** and **gcl mRNAs**; RNA-binding maps in vitro to the C-terminal domain of **Oskar**
* The highly conserved N-terminal domain forms dimers and mediates **Oskar** interaction with the germline-specific **RNA helicase Vasa**.
* **Oskar** localizes **nanos mRNA** at the extreme posterior pole of the unfertilized egg
48
role of nanos
* mRNA and protein binding protein
* translational repressor of maternal mRNAs
* role in AP patterning and germ plasm assembly
49
**What is the role of *pgc*?**
* ***pgc*** = polar granule component
* Required for maintanance of Primordial Germ Cells (**PGCs**)
* so what is the role of the ***pgc*** protein in **PGC** formation?
* **PGCs** are transcriptionally silenced by the ***pgc*** gene product
