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Cell Bio Exam > Invert dev - new > Flashcards

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
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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
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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.

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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
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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
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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
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7
Q

List the 5 vulval development steps

A
  1. generation of VPCs
  2. Vulval precursor patterning
  3. generation of adult cells
  4. Anchor cell invasion
  5. Morphogenesis of vulva
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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
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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
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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
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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
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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
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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
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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:

  1. Retarded: semidominant mutant, is seen in T-lineage
    1. in L2 stage, T.ap generates a cell division pattern and ascendent cell types similar to those normally generated during L1 by T cell.
  2. Precocious: in recessive lin-14 mutant
    1. T cell precociously generates cell division pattern normally generated during L2 by T.ap
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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
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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
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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
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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
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19
Q

How can GFP be useful in fly genetics

A

Can be inserted into genome to trace cells in space and time

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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
Q

Describe segment polarity genes

A
  • Segment polarity: denticle are duplicated in a mirror image
    • Hedgehog, Wnt signaling
    • Mutation leads to segments not being properly separated
26
Q

What are Cis-regulatory elements?

A
  • 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
Q

How is patterning information coded in cis-regulatory elements?

A
  • 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
Q

Describe Bicoid mutants

A
  • 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
Q

What are the different types of genes needed for embryonic development and a good analogy for them?

A
  • “realisator” genes (“workers”)
  • “selector or architect” genes (“architects”) that coordinate and regulate the realisator
30
Q

Define an imaginal disc

A
  • Proginator tissue in larvae from which adult tissues develop
  • Example: wing imaginal disc corresponds to a developing hemi-thorax and a wing
31
Q

Give a brief summary of the stepwise process in terms of gene progression (imaginal disc to adult structure)

A
  • 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
Q

describe step 1 of the notum development

A
  • 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
Q

describe step 2 of the notum development

A
  • 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
Q

describe step 3 of the notum development process

A
  • 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
Q

describe step 4 of the notum development process

A
  • 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
Q

describe step 5 of the notum development process

A
  • 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
Q

Which genes are important in development of wing primordium?

A
  • 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
Q

To which segments is the wing primordium restricted, and how?

A

T2 and T3 by HOX genes

39
Q

Purpose of clonal analysis

A
  • 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
Q

How can cells be modified to grow faster in clonal analysis and why does this help?

A
  • 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
Q

how is compartmental identity defined?

A
  • The compartmental identity is defined by expression of the selector genes
    • Engrailed: Posterior
    • Apterous: dorsal
42
Q

What does Dpp do?

A
  • 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
Q

How can a cell undergo mitosis and at the same time retain a stem cell state?

A
  • 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
Q

4 steps in the life cycle of a germ cell and the processes that affect germ cell formation and maintenance

A
  • Germ cells first have to be specified = Primordial Germ Cells (PGCs)
  • 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
Q

What is the function of germ plasm?

A
  • 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
Q
  • Name 5 maternal mRNAs localized to the germ plasm and necessary for germ cell formation (8 total, 5 important ones to remember)
A
  • Oskar
  • Nanos
  • Vasa (conserved germ cell marker)
  • Pole granule component (pgc)
  • Trapped in endoderm-1 (tre-1)
  • Tudor
  • Pumilo
  • Germ cell less (gcl)
47
Q

What is the role of Oskar in germ plasm formation?

A
  • 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
Q

role of nanos

A
  • mRNA and protein binding protein
  • translational repressor of maternal mRNAs
  • role in AP patterning and germ plasm assembly
49
Q

What is the role of pgc?

A
  • 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

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