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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
Q

What does it signify if types of genes turned on are dependent on the distance from the source cell?

A

morphogen is functioning

26
Q

In a signal transduction cascade, what does a cytoskeleton effector protein do?

A

alter cell shape or movement

27
Q

In a signal transduction cascade, what does a gene regulatory effector protein do?

A

alter gene expression

28
Q

In a signal transduction cascade, what does a metabolic enzyme effector protein do?

A

alter metabolism

29
Q

How is a signaling cascade initiated?

A

Extracellular signaling molecule binds to receptor

Receptor undergoes conformational change

30
Q

What are three molecules in the TGFb (Transforming Growth factor b) signaling pathway?

A

TGFb
BMP
Nodal

31
Q

Describe the TGFb signaling pathway

A

secreted molecules (TGFb, BMP, Nodal) bind receptors
Smad proteins are phosphorylated
Smad proteins enter nucleus and modulate txn

32
Q

What is the sonic signaling pathway involved in?

A

development

33
Q

Describe the sonic hedgehog signaling pathway

A

SHH binds PTCH receptor
SMO no longer inhibited
GLI-mediated txn activated

34
Q

what happens in the absence of the SHH

A

PTCH protein inhibits SMO

GLI-mediated txn is repressed

35
Q

Antagonistic activities of what two signaling pathways pattern the developing spinal chord?

A

SHH and Wnt/BMP

36
Q

What patterns the neural tube?

A

morphogen gradients of SHH And Wnt/BMP

37
Q

What is situs solitus?

A

Normal orientation of internal organs

38
Q

What is situs invertus totalis?

A

complete mirror reversal of organ LR asymmetry

39
Q

What is heterotaxy or situs ambiguus?

A

LR asymmetry of a subset of organs

40
Q

What does heterotaxy result it?

A

congenital malformations

41
Q

what is asplenia?

A

right isomerism heterotaxy - two of the right side

42
Q

what is polysplenia?

A

left isomerism heterotaxy - two of the left side

43
Q

what congenital diseases can come with LR asymmetry (heterotaxy)?

A

congenital heart defects
asplenia or polysplenia
malrotaton of intestine, volvulus

44
Q

What is volvulus? What does it result from?

A

twisted bowl –> obstruction

from heterotaxy

45
Q

What are the steps in the development of cardiac LR asymmetry?

A

L and R-sided bilateral heart fields fuse to form linear heart tube
rightward cardiac looping
growth, additional shaping

46
Q

what does rightward cardiac looping achieve?

A

aligns chambers and vascular connections

47
Q

What gene is expressed asymmetrically in the organizer/node region during development in mice, chicks, frogs, and zebrafish?

A

Nodal

48
Q

what are the three symptoms of Kartagener’s syndrome?

A

immobile sperm –> infertile
chronic bronchitis and sinusitis
some have inverted internal organs

49
Q

What is immobile in Kartagener’s syndrome?

A

cilia

50
Q

Based on Kartagener’s syndrome, how is asymmetry achieved during embryogenesis?

A

asymmetric fluid flow from cilia establishes morphogen gradient

51
Q

Describe the Nodal signaling cascade in the lateral plate mesoderm

A

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
Q

Where is transcription factor Pitx2 found? What is it thought to do?

A

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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