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MCP Unit 2 > Lecture 6: Mechanisms of Development > Flashcards

Lecture 6: Mechanisms of Development Flashcards

1
Q

What mechanisms drive development?

A

Genes

cell-cell communication

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2
Q

what is a homologous gene?

A

a gene similar in structure, evolutionary origin, and likely function, to a gene in another species

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3
Q

What is the concept of genomic equivalence?

A

all somatic cells have the same chromosomes (set of genes) as all other somatic cells

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4
Q

What does somatic nuclear transfer mean?

A

cloning

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5
Q

What does somatic nuclear transfer provide evidence for?

A

genomic equivalence (all cells have same genes)

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6
Q

In the first cloning project, what was fused?

A

nuclear donor: mammary gland cell nucleus

oocyte donor: enucleated oocyte

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7
Q

T/F: The nuceli of adult somatic cells contain all of the genes necessary to generate an adult organism

A

True

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8
Q

What is the concept that says the genetic material is the same in every cell, but only a small % of the genome is expressed in each cell type?

A

Differential gene expression

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9
Q

What are the four levels of gene expression regulation?

A

differential gene expression
selective nuclear RNA processing
selective mRNA translation
differential protein modification

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10
Q

What technique is used to determine the locations of mRNA expression?

A

RNA in situ hybridization

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11
Q

What are the 4 cellular processes through which differential gene expression is achieved?

A
  1. cell proliferation - producing many cells from one
  2. cell specialization - creating cells with different characteristics at different positions
  3. cell interactions: coordinating the behavior of one cell with that of its neighbors
  4. cell movement: rearranging cells to form structured tissues and organs
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12
Q

In cell induction, what do the inducer and responder do?

A

inducer - provides signal which changes behavior of target tissue
responder - tissue being induced

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13
Q

what must the responder have in cell induction?

A

competence - ability to respond to signal

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14
Q

What is an example of a cell induction system?

A

optic vesicle inducer

Xenopus laevis

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15
Q

How does the optic vesicle inducer in Xenopus work?

A

optic vesicle inducer indices lens formation in the anterior (head) portion of the ectoderm
cannot do so in the trunk or abdomen (tissues are not competent)

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16
Q

In the optic vesicle inducer in Xenopus, what happens if the optic vesicle is removed?

A

Surface ectoderm forms abnormal lens or no lens

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17
Q

What role does Pax6 play in Xenopus?

A

makes ectoderm competent to respond to signals from the optic vesicle (inducer)

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18
Q

What is the competence factor in Xenopus’s optic vesicle induction?

A

Pax6

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19
Q

What does a homozygous loss of Pax6 lead to?

A

fatal

almost complete failure of entire eye formation

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20
Q

What is aniridia?

A

heterozygous mutation to Pax6
not fatal
ocular defects

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21
Q

What is juxtacrine signaling?

A

contact between inducing and responding cells

22
Q

what is paracrine signaling?

A

diffusion of inducers from one cell to another

23
Q

what are morphogens?

A

paracrine signaling moleculces which cause concentration-dependent effects

24
Q

How was the morphogenic property of Nodal identified?

A

Nodal mRNA injected into embryo
nodal protein is produced - secreted, allowed to signal
mark particular regions/structures, analyze induction

25
What does it signify if types of genes turned on are dependent on the distance from the source cell?
morphogen is functioning
26
In a signal transduction cascade, what does a cytoskeleton effector protein do?
alter cell shape or movement
27
In a signal transduction cascade, what does a gene regulatory effector protein do?
alter gene expression
28
In a signal transduction cascade, what does a metabolic enzyme effector protein do?
alter metabolism
29
How is a signaling cascade initiated?
Extracellular signaling molecule binds to receptor | Receptor undergoes conformational change
30
What are three molecules in the TGFb (Transforming Growth factor b) signaling pathway?
TGFb BMP Nodal
31
Describe the TGFb signaling pathway
secreted molecules (TGFb, BMP, Nodal) bind receptors Smad proteins are phosphorylated Smad proteins enter nucleus and modulate txn
32
What is the sonic signaling pathway involved in?
development
33
Describe the sonic hedgehog signaling pathway
SHH binds PTCH receptor SMO no longer inhibited GLI-mediated txn activated
34
what happens in the absence of the SHH
PTCH protein inhibits SMO | GLI-mediated txn is repressed
35
Antagonistic activities of what two signaling pathways pattern the developing spinal chord?
SHH and Wnt/BMP
36
What patterns the neural tube?
morphogen gradients of SHH And Wnt/BMP
37
What is situs solitus?
Normal orientation of internal organs
38
What is situs invertus totalis?
complete mirror reversal of organ LR asymmetry
39
What is heterotaxy or situs ambiguus?
LR asymmetry of a subset of organs
40
What does heterotaxy result it?
congenital malformations
41
what is asplenia?
right isomerism heterotaxy - two of the right side
42
what is polysplenia?
left isomerism heterotaxy - two of the left side
43
what congenital diseases can come with LR asymmetry (heterotaxy)?
congenital heart defects asplenia or polysplenia malrotaton of intestine, volvulus
44
What is volvulus? What does it result from?
twisted bowl --> obstruction | from heterotaxy
45
What are the steps in the development of cardiac LR asymmetry?
L and R-sided bilateral heart fields fuse to form linear heart tube rightward cardiac looping growth, additional shaping
46
what does rightward cardiac looping achieve?
aligns chambers and vascular connections
47
What gene is expressed asymmetrically in the organizer/node region during development in mice, chicks, frogs, and zebrafish?
Nodal
48
what are the three symptoms of Kartagener's syndrome?
immobile sperm --> infertile chronic bronchitis and sinusitis some have inverted internal organs
49
What is immobile in Kartagener's syndrome?
cilia
50
Based on Kartagener's syndrome, how is asymmetry achieved during embryogenesis?
asymmetric fluid flow from cilia establishes morphogen gradient
51
Describe the Nodal signaling cascade in the lateral plate mesoderm
asymmetric signals (Ca2+ ion) respond to cilia-driven fluid flow signals trigger nodal expression in left lateral plate mesoderm Nodal induces txn of Pitx2 (txn factor) and Lefty (Nodal inhibitor)
52
Where is transcription factor Pitx2 found? What is it thought to do?
left side of developing heart, gut, and brain | regulate expression of genes which mediate asymmetric organ morphogenesis

MCP Unit 2 (17 decks)

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