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BoC > Easter > Flashcards

Easter Flashcards

1
Q

Define secondary messengers

A

Small molecules that are formed/ released into the cytosol in response to an extracellular signal. Helping to relay the signal to the interior of the cell

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2
Q

What enzymes are active in the dark in relation to growth in plants?

A

PIF3 active
HY5 broken down by COP1
Etiolation

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3
Q

What enzymes are active in the light in relation to growth in plants?

A

PIF3 broken down by Pfr
HY5 active
Normal growth of hypocotyl

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4
Q

What are the 2 types of G proteins?

A

Heterotrimeric (3 subunits, e.g. adrenoreceptors)
Monomeric (Ras proteins, 1 subunit)

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5
Q

How are low concentrations of Ca2+ maintained within a cell?

A

Ca2+ ATPase pumps out
SERCA pumps Ca2+ into ER
Na/Ca2+ antiporter

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6
Q

Describe the differences between embryonic and somatic cell cycles in animals

A

Embryonic don’t grow in size, just divide
Embryonic don’t have G1 and G2 phases for some time leading to faster replication
Drosophila have nuclei that divide and replicate and locate themselves near a membrane but aren’t separated for a while
Embryonic don’t go under cell cycle arrest
Embryonic is synchronous division unlike somatic which is asynchronous
Somatic cells can undergo differentiation

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7
Q

What is the French flag model of pattern formation?

A

Model proposed by Lewis Wolpert
Suggests that gradients of morphogen effect pattern formation
Cells exposed to higher concs of morphogen will evolve into different cells than those experiencing lower concs
In terms of flag blue- high conc
Also shows how positional information can be established by using a gradient

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8
Q

What are DELLA proteins?

A

TFs that stop plant growth
Bind and stop the expression of certain growth genes . Bind to PIF3
Controlled by Gibberellins which when present binsd to DELLA and destroys it
Important in plant response to environment

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9
Q

What is the role of Vg1?

A

Induce the formation of endodermal cells
Induce formation of mesodermal cells
Defining posterior-anterior axis
Migration and differentiation of cells

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10
Q

How would you generate a fate map of a developing amphibian embryo? What can fate maps tell you about embryo development?

A

Use a fluorescent dye (tracer)
Inject into a single cell of the embryo
Follow the tracer to see what the cell form that area develops into
Use- tells us what part of the body that area of the embryo will give rise to

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11
Q

What is the Zone of Polarising Activity? Outline how the ZPA contributes to limb development

A

Located at the posterior end of the limb
How long cells remain in the zone determines their fate
Sonic hedgehog (SHH) is a morphogen present in the area
Most distal cells, remaining in ZPA the longest will turn into digits
SHH used to receive positional information
Can be tested by injecting SHH into another area (e.g. anterior)

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12
Q

What are homeotic mutations? Give one example each for a homeotic mutation in an animal and in a plant. Outline basic similarities and differences between animal and plant homeotic genes in terms of genomic arrangement and protein structure

A

Homeotic mutations are changes in the DNA which lead to the formation of a whole body part in the wrong place. CLEANLY TRANSFORMED.
e.g. Drosophila Ubx, has 2 pairs of wings because another pair grew instead of halteres
e.g. Agamous in plants, where petals grow in place of stamen
Similarities
- cleanly transformed
- both genes control identity and position of developing segment
Differences
- different genes involved plants (MADS-box) animals (Hox)
- so different protein structure

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13
Q

Describe how quorum sensing controls bioluminescence in Vibrio fischeri.

A

Quorum sensing is dependent on population density of bacteria
Bioluminescence is only expressed by luxAB genes when the critical population density is reached
1) Signal is OHHL produced by LuxI
2) When critical density reached OHHL is sensed by LuxR
3) LuxR activates LuxAB and LuxI (positive feedback)

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14
Q

Briefly describe two examples of signalling processes in eukaryotes that use cytosolic receptor proteins to detect the initial stimulus molecule

A

Steroid hormone signalling uses cytosolic receptors because the hormone can diffuse through the plasma membrane e.g. oestrogen. Bind to steroid hormone receptors
Retinoic acid receptors- for signalling using retinoic acid from Vit A

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15
Q

Describe briefly experiments that test for pluripotency of cells and pluripotency of their nuclei

A

1) Teratoma formation assay- Inject pluripotent stem cells or iPSCs into an immunocompromised cell. Leave to grow and if pluripotent will form all 3 germ layers and differentiate to form a teratoma (tumour)
2) Somatic Cell Nuclear Transfer
- transfer the nucleus of a somatic (differentiated) cell to a enucleated oocyte. If a whole organism can form from the cell then shows pluripotent characteristic

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16
Q

What happens at the mid-blastula transition in the Xenopus?

A

-Transition from rapid cell division to activation of zygotic gene expressions and embryo development
-The cell begins to divide under the control of zygotic determinants
-Previously under the control of maternal determinants that sets the poles and axes in the embryo
- Increase in cell size, cells allowed to grow before dividing again, due to G1 and G2 phase (cell division cycle is now slower)

17
Q

How does phytochrome mediate responses to the environment?

A
  • Detects the amount of red and far ref light
  • Pr is inactive (cis) form, Pfr is active (trans) form
  • So detects changes in light in the environment, which controls development. E.g. long periods of light cause etiolation , where DELLA is broken down and the plant grows in search of light
18
Q

Give examples of how embryonic polarity and cell type specification can occur through cytoplasmic determinants. How is RNA encoding the determinant localised to the appropriate part of the embryo?

A

Specific molecules that effect transcription and so cell fate are present in the cytosol
In Drosophila- maternal determinants
Bicoid= anterior- posterior
Dorsal= dorsal-ventral axis
^^Localized by the 3’UTR

19
Q

Describe how cAMP acts as the aggregation stimulus in Dictyostelium discoideum

A
  • cAMP acts as an aggregation stimulus
    -Cells secrete cAMP when in stress conditions, creating a gradient
    -This gradient is used for chemotaxis and movement
  • Directs Dictyostelium to aggregate together
  • cAMP also allows for intracellular communication, as the cAMP pathway is activated
  • cAMP also activates PLC pathway via GPCRs on the membrane
20
Q

Give two examples where the roles of developmental regulatory genes are conserved between vertebrates and invertebrates

A

Hox genes are conserved
- role is to identify body plan and control spatial organisation
Pax6 gene
- TF that plays a role in eye development, formation of lens and other structures

21
Q

In what ways does plant development differ from that of animals?

A

Animal development, before the MBT is controlled by maternal determinants which are not present in plants
Plants don’t undergo gastrulation, instead form meristems
Plant always growing and developing, greater plasticity than animals
Plants have longer term developmental response to environment, e.g. gravitropism or phototropsim, animals have a more immediate change

22
Q

How does abscisic acid induce closure of stomata?

A

ABA stops the function of H+ ATPase
Promotes the efflux of Cl-
Causing water to move out of the guard cell
Closing the stomata

23
Q

How are pseudopodia localised appropriately in the Dictyostelium chemotaxis response?

A

Founder cells secrete cAMP which leads to chemotaxis
cAMP detected by Gs proteins activating cAMP pathway
Positive feedback loop with further cAMP release
PLC pathway leads to IP3 and DAG
Releases Ca2+ from ER
Causes change in cytoskeleton shape (movement)
PDE degrades cAMP so gradient of cAMP can be detected

24
Q

What is the role of the inositol (1,4,5) tris phosphate receptor (IP3R) in the fertilisation of star fish eggs?

A

IP3 activated when sperm fuses to the egg
Binds to IP3R on the ER
Causes Ca release
- Cortical reaction
-initiation of embryo development

25
Q

Briefly describe how the myogenic differentiation (MyoD) gene was discovered

A
  • Compared the gene expression before and after of an embryonic turned muscle mouse cell
  • Identified a gene that was activated (MyoD)
  • Introduced MyoD into a fibroblast (doesn’t express the gene commonly)
  • Led to the formation of muscle cell from the fibroblast
26
Q

How could you experimentally test if the sequence responsible for the localisation of an mRNA to the anterior of the developing Drosophila egg (oocyte) is in the 3’UTR (untranslated region)? Briefly describe one experiment and one control

A

Use Drosophila Oocyte
1) Extract RNA from the ocoyte
2) PCR amplify the 3’ UTR
3) Insert UTR into vector with fluorescent tag
4) Use vector to infect
5) Using fluorescence microscopy monitor the location of the fluorescence
Control- infect cell with a vector that has fluorescent tag but no UTR

27
Q

How could you test the role of UTRs in developing poles?

A

UTR swap- replace 3’UTR with another UTR which localizes it to a different region, inject the mRNA into the cell. Control- with injections of mRNA in different locations, mRNA with difference UTR sequences
Mutagenesis Assay- Mutate the 3’ UTR by point mutations, inject the mutated mRNA into the cell. Follow development of poles

28
Q

What is the role of the 3’UTR in development?

A

1) mRNA localization to cause asymmetry in development
- moves mRNA along the cytoskeleton
- bicoid to anterior, and oskar to posterior
- tracked by GFP
2) Increases mRNA stability

29
Q

How can axes in an embryo be determined?

A

External and internal environments
1) 3’ UTR (Maternal determinants)
- moves and localises mRNA
- Oskar posterior, bicoid anterior
2) Ca2+ in fucus
- movement of Ca2+ through a cell can lead to polarisation
- influx=basal, efflux = apical
3) Sperm entry
- relocation of mRNA e.g. Wnt11
- 30 degree cortical rotation
4) Cell-cell interactions
- Transforming growth factor regulating gastrulation
- concentration gradients controlling limb division and formation

30
Q

What sets the apico-basal axis of the plant embryo, for example in Arabidopsis?

A

Polarity due to the location of mRNAs and proteins present in the embryo
Gradients from an axis to another across an embryo informs cells about their location
Arabidopsis- creates an auxin gradient , transport occurs from apical to basal

31
Q

Outline the Notch signalling pathway

A
  • Short distance communication
    Span the membrane once and contain ligand binding site
    Binding causes conformational change
    ADAM class proteases cleave at specific site
    Intermediate peptide further cleaved by gamma secretase
    Releases NICD, which binds to transcription factors
  • important in development of nervous systems and central vulva in C.elegans
32
Q

What are TGF- beta family proteins?

A

Transforming growth factors
- regulate stages of the cell cycle
- acts as a tumour suppressor
- has many roles in regulating transcription

33
Q

What are the 3 segmentation genes in Drosophila?

A

Gap genes- mutations leads to gaps in the segmentation of the body
Pair-rule genes- result in zebra stripe pattern, leads to alternating pattern, mutation doesn’t
Homeotic Selector- specify what structures form in what segment

BoC (4 decks)

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