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regulation of maternal Hb vs. zygotic Hb.    
Bicoid protein on the anterior end promotes transcription of zygotic Hb.  On the posterior end Nanos blacks translation of the maternal Hb mRNA.  
Role of Spatzle  
  • Spatzle acts through nuclear localized transcription factor Dorsal, which induces ventral fates. 
  • Spatzle also contros production of Dpp which induces dorsal cell fates. 
Gurken and Pipe  
  • Gurken protein only acts on dorsal follicle cells, and it inhibits the synthesis of pipe on dorsal side.
  • on the ventral side, in the absence of Gurken, pipe is synthesize, triggering a proteolytic cascade.  
Dorsal activation of gene expression    
  • Dorsal is highest [] in ventral region. 
  • at high concentrations dorsal protein binds to the 3 low affinity dorsal binding sites induces transcription of twist. 
    • so twist is expressed most ventrally.
mechanism nanos translational inhibition of hb in posterior region    
in the posterior: Nanos protein forms a complex with two other molecules and binds to a nanos response element (NRE) located in the hb mRNA --> binding inhibits translation via deadenylation.  
bicoid vs. caudal  
  • basically the same as posterior inhibition of hb translation by nanos.  only this is anterior inhibition of caudal translation by bicoid protein.
  • bicoid and caudal form gradients of opposite polarity. 
pair rule genes  
there are 14 segments in drosophila, and pair rule genes are expressed in 7 stripes, each separated by "interstripes" where no pair rule genes not exressed 
what are activators of eve (even skipped) transcription? repressors?  
  • activators: bicoid and hunchback.
  • repressors: Kruppel and Giant. 
the coordinated regulation of the repressors and activators determine the boundaries of the eve stripe 2. 
what influences the boundaries between stripes and interstripes?
each stripe is formed in response to a different combination of transcriptional regulators acting on a specific area. 
what are the 3 extracellular signaling pathways that are used to create boundaries b/t cell types?

1. pathway activated by Hh

2.  wingless

3.  TGFb (transforming growth factor)  


How does Chordin's affect TBFb signaling.  
  • chordin binds to BMP4 which inhibits it from binding to receptor.  But this inhibition is relieved byt he presence of Tolloid (or xolloid) protease which is specific for the cleavage and degradation of chordin, releasing BMP4 and allowing it
What are some differences in the 3 TGFb receptors?
  • TGFIII concentrats TGFb near the cell surface and facilitates type I and II signaling. 
  • Binding of TGFb induces formation of a tetramer comples (2 type I and 2 type II)
  • type I and II both have transmembrane serine/threo
what are the 3 types of smads? what is their role in TGFb signaling?

1.  three types are a R Smad (receptor regulated), co-Smad, and an I Smad (inhibitory) 

2.  Receptor binding causes R Smad to be phosphorylated (activated).  Now it binds to a co-Smad, and this complex can not enter the nucle

what are the 2 types of cell-cell communication?

1.  Reciprocal Induction: (positive feedback mechanism)  --> two cells with distinct fates send and receive signals b/t them that induce further differentiation.

    ex: ephrin-B2 (on ar

What is the mechanism of Notch/Delta signaling pathway? What type of cell-cell communication does it result in? 

[notch acts as receptor.  Delta acts as ligand]

  • interaction b/t delta and notch triggers proteolytic cleavage of Notch, which allows it to translocate to nucleus and activate transcription.  This inhibits Delta transcription.
what are the 3 layers of protection that we have from pathogens?

1.  skin: acts as a mechanical barrier

2.  innate response:  this is the immediate response.  also this is what sends out signals to induce the adaptive response.  

3.  Adaptive immunity:  this is specifi

what are some differences b/t the innate and adaptive response?    

1.  Kinetics:  onset of innate is much faster.  The adaptive response might take a few days 

2.  Specificity:  The adaptive responds to specific pathogens.  

3.  Memory:  the adaptive can build m

What are 3 types of complement activation pathways?  

1.  Classical (requires antigen:antibody immune complex for initiation)

2.  alternative: can be induced by spontaneous generation of C3.

3.  Mannose Binding Lectin (MBL) pathway:  specifically recognizes mannose sugars o

What role does the membrane attack complex play in complement pathways?    
C5 recruits c6-c9 to pathogen cell membrane and punches a hole.  This allows free passage of solutes and water across membrane, and causes cell lysis.  
How do macrophages and NK cells regulation each other?

positive feedback loop:  NK cells produce IFN-gamma, which enhances macrophage killing and induces macrophages to produce more IL-12 which promotes proliferation of NK cells (which leads to more IFN-gamma)

macrophages also secrete TNF.  

which Ig play a role in complement activation?    
IgM and IgG
Which Ig is associated with hypersensitivity reactions?  And what role do mast cells play in those reactions?


mast cells release histamines upon activation by igE and antigen.  This causes localized vascular permeability leading to inflammation.   

what are the 4 cardinal signs of inflammation?  

1.  redness (rubor)

2.  swelling (tumor)

3.  heat (calor)

4.  Pain (dolor) 

What are the 2 stages of B cell development and where do they each occur?    

1.  antigen independent development and this takes place in the bone barrow stromal cells.  it leaves this stage as an immature B cell expressing IgM. 

2.  antigen dependent developmen

what is the difference between membrane and secreted forms of Ig?    
  • membrane bound Ig are attached to the surface of B cells and produce antibodies.  
  • secreted Ig are found in the plasma, interstitial fluid in tissues, secretory fluids and bound to the surface of eff
What are some general properties of MHC class I molecules  
  • closed binding site, so less flexibility in the peptides that can bind (7-11 amino acids long)
  • MHC I present pathogens to CD8 cytotoxic T cells.
  • structurally they have a b2-microglobulin chain that is not polymorphic. 
what are some general characteristics of MHC class II molecules? 
  • expressed primarily on immune cells like macrophages and dendritic cells.
  • it has an open peptide binding region so can accommodate bigger peptides than MHC I, (13-17aa long)
  • MHC II molecules deliver peptides originating from endocy
CD 4 T cells can further divide ito TH1 cells and TH2 cells.  What are their functions?
  • TH1: these activate macrophages by secreting cytokines that recuit them to site of infection
    • big role in inflammatoryresponse.
  • TH2: involved in stimulating B cells to produce certai
What cytokines are secreted by TH1 cells? TH2 cells?

1.  TH1 cells secreteIL-2, IFN-gamma, and TNF (think of inflammatory response, and these are the same cytokines macrophages release)

2.  TH2 cells secrete IL-4, IL-5 and IL-10.   

What three amino acids contribute to thetripple stranded helical structure of collagen?

collagen has a high concentration of

proline 11%, glycine 30%, and hydroxyproline 10%

the proline and hydroxyproline contribute to helical portion, and the glycine contributes to the axis points in the swival.  

What happens in non enzymatic glycosylation? 
This occurs frequently in diabetics --> excess bld sugar binds to the basal lamina (type IV collagen) and disrupts collagen structure and impairs its ability to filtrate.  
In the first post translational modification of collagen what enzymes, and cofactors are involved? What is produced in this step?

1.  Hydoxylation

  • Enzyme: prolyl Hydroxylase
  • cofactors: oxygen, vitamin C and Iron

Gly-Pro-Pro -------> Gly-Pro-OHPro (hydroxyproline)


what is the precursor to collagen and where does synthesis occur?
  • procollagen is the precursor.  Synthesis starts in the ER.  
After hydroxylation of collagen what is the next post translational modification? what enzymes and cofactors are required?

2.  Glycoslyation

  • Enzyme:  Galactosyl transferase
  • cofactors: Mn

Gly-Pro-OHLys --> Gly-Pro-OHLys-Gal-Glu

Galactose then glucose added&n

What are the 3 critical processes in procollagen processes?

1. Registration: in C domain, inter and intra disulfide bonds.  These extension peptides make sure that proper alignment occurs for correct helical formation

2.  Solubility:  N domain, ha

Once collagen is in extracellular matrix what post translational modification occurs?
  • modification by lysoloxidases (w/ cofactor copper) forms stable cross links b/t inter/intra molecules. 
  • This step is essential for strength.  In this state it is very resistant to proteolytic degradation.  
what are the three functional classes of cell junctions?

1.  occluding junctions (or tight junctions)

2.  Anchoring junctions

3.  Communication junctions (gap junctions) 



Where are the 3 cell junctions types located in relation to the apical and basal surface?
  • Tight junctions are located on apical side right below the microvilli

  • gap junctions are located along the lateral surfaces of adjacent cells.
  • anchoring junctions
Describe the function of tight junctions.
  • Tight junctions form an impermeable barrier b/t two cells (like the lumen and gut).  To cross this, molecules need to be actively transported to get to other side.
  • They help establish and maintain polarity by preventing diffusi
what is the molecular structure of Gap junctions?
  • These junctions are comprised by clusters of channels between two plasma membranes. 
  • channels are composed of connexons
  • these direct connections allow for communication of material b/t cells. 
What structures comprise the basal lamina?
  • Type IV collagen: this is the main component of all basal laminas. 
  • Laminin:  this is a family of multiadhesive proteins that form a fibrous 2 dimentional network b/t type IV collagen.&nbs
What are the 3 mechanism of wound repair? 

1.  Connective tissue deposition: formation of new collagen and proteoglycans at wound site, which form the scar tissue

2.  Epithelization: epithelial cells migrate across damage site and proliferation.

What are the 4 stages in wound healing?

1.  Hemostasis:  materialreleased from platelets from fibrin to form a clot. 

2.  Inflammation:  begins soon after injury, selectins bind to PMNs, marginization.  Inflammation invol

Post translational modification: collagen degradation and remodeling. 
  • Matrix Metallo-peoteinases (MMPs) need trace metal Zn.
    • these degrade denatured collagen.  Its synthesized as procollaginase (inactive) and needs to be cleaved to be active. 
  • Tissue
What are some differences between desmosomes and hemidesmosomes?
  • desmosomes are anchoring junctions b/t two cells.  They use cadherins as their adhesion protein
  • hemidesmosomes are anchoring junctions b/t cell-matrix.  They use integrins as their adhesion prote
What are the differences between focal adhesions and hemidesmosomes in cell-matrix junctions?

(both consiste of clustered integrin molecules):

  • the extracellular domain of integrins in a focal adhesion binds to Fibronectin
  • the extracellular domain of integrins in hemid
What is the RGD sequence?
This is a sequence found on fibronectin that mediates binding to integrin proteins. 
What are the two basic steps in myogenesis?

1.  Determination: precursors cells become committed to a particular developmental pathway (but don't exhibit the characteristics of differentiated cells yet)

2.  Differentiation:  the committe