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Cell and Developmental biology > mesoderm induction > Flashcards

mesoderm induction Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

what is the antero-posterior axis

A

head to tail

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2
Q

what is the dorso-ventral axis

A

back to belly

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3
Q

left to right

A

more or less bilateral to symmetry

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4
Q

in frog and fish what is the vegetal axis controlled by

A

maternal factors, the axis is already manifest in the unfertilised egg

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5
Q

when is Vg1 protein produced

A

after fertilisation

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6
Q

what are Vg1 and signalling protein Xwnt11 required for

A

establishment of dorso-ventral axis, early mesoderm formation and specification of dorsal character

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7
Q

where is the mRNA of vegetally localised protein in Vg1

A

in the vegetal half of the egg, it becomes further restricted to vegetal cell cortex

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8
Q

how is the dorsal ventral axis established

A

through sperm entry - this leads to cortical rotation

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9
Q

what is cortical rotation

A

when the layer below the cell membrane shifts 30 degrees toward the future dorsal side, subcortical microtubules become reorientated with plus ends pointing away from the site of sperm entry this makes tracts for direct transport of proteins and mRNAs

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10
Q

what does cortical rotation lead to

A

transport of vegetally localised molecules to future dorsal side - opposite to sperm point of entry

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11
Q

what happens if cortical rotation fails

A

failure of the dorsal anterior stuctures

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12
Q

what is the signalling centre in the dorsal vegetal region called and what is it required for in development

A

the Nieuwkoop centre is required for development of dorsal structures

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13
Q

what happens when you transplant the Nieuwkoop centre

A

it induces the ectopic body axis and a twinned embryo will form with duplicated axis

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14
Q

what does Wnt-B-catenin promote

A

formation of dorsal stuctures

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15
Q

what ligand mediates signalling activities for dorsal character

A

Wnt

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16
Q

what happens when Wnt ligand is stimulated

A

degradation of beta catenin is degraded which leads to the transduction of Wnt signalling to the nucleus where it regulates gene transcription factors of TCF family

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17
Q

what happens if wnt or vg1 is misexpressed

A

2 embryonic axes containing dorsal structures form

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18
Q

qwhat does the combined action of Wnt and other maternally derived signals lead to

A

the formation of the nieuwkoop centre in the dorsal vegetal region

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19
Q

what is the chick equivalent of the nieuwkoop centre and what is it determined by

A

the posterior marginal zone - determined by gravity

20
Q

do maternal factors play are role in chick body axis establishment

A

no

21
Q

what does the formation of the posterior marginal zone lead to

A

it is the first symmetry break event in the chick blastoderm and provides signals that leads to the formation of the primitive streak - at the top of the streak is the organiser region (Henson’s node)

22
Q

how is the primitive streak induced in chick

A

it involves the removal of signals from the hypoblast that inhibit streak formation
the hypoblast must be replaced by the endoblast so streak formation can start

23
Q

what is a fate map used for

A

to understand how germ layers and their derivatives arise - it is important to know which cells give rise to the distinct cell types

24
Q

how are fate maps used

A

labelling of cells or single cells at an early stage during development to see what regions they develop into

25
Q

what determines cell types

A

signal factors

26
Q

what are fate maps of vertebrates

A

variations of basic body plans

27
Q

what info do fate maps not give you

A

the full potential of the cells or if they are commited

28
Q

what happens when the presumptive eye region is transplanted

A

an eye still develops as the cells are committed

29
Q

what signals specify the germ layers in frog embryo

A

induction takes place when one signal produced by a cell group promotes a change of fate in responding cells
frogs mesoderm is induced in the ectoderm by signals from the vegetal region

30
Q

how is the mesoderm induced

A

in ectoderm cells by signals from the vegetal region

31
Q

what makes up the ectoderm

A

explants from the blastula stage of the embryo animal caps

32
Q

where are the mesoderm derivatives formed

A

cells from the marginal zone where the animal cap cells oppose the vegetal cells

33
Q

what does labelling explant confirm

A

if explant cells are labelled before combination with vegetal cells, it is shown they are needed for mesoderm

34
Q

what is the community effect

A

it ensure the development of all cells within an embryo, a critical number of cells are required for response to mesoderm inducing cells

35
Q

what is the cell fate indicated by

A

neighbouring cells

36
Q

when does mesoderm induction take place

A

within a competence period, the cells are able to be induced from the mesoderm for 7 hours
2 hrs of inducing signal during this period is sufficient for mesoderm formation

37
Q

what patterns the mesoderm

A

distinct inducing properties of dorsal and ventral vegetal cells
dorsal vegetal cells induce muscle and notochord from animal cell caps

38
Q

what do dorsal vegetal cells induce

A

dorsal vegetal cells induce muscle and notochord from animal cell caps

39
Q

what do vegetal signals induce

A

the mesoderm, nieuwkoop centre and induction of the organiser

40
Q

what inhibits the patterning of the ventral mesoderm

A

signals from dorsally located organiser

41
Q

what inhibits mesoderm formation

A

blocking of signals through the TGFB receptors, leads to no mesoderm or axial structures

42
Q

what is the negative dominant approach to blocking signals through TGFB receptors

A

no signal from the mutant receptor even when dimerised with wild type receptor so mRNA encoding the mutant receptor is injected into both cells of a two cell embryo
no mesoderm or axial structures form

43
Q

how does varying concentrations of activin affect expression and gene cohorts

A

genes expressed by ectodermal cells in response to increased conc of activin
low = keratin
med = Brachyury
high = gooseloid organiser

44
Q

what does cells close to activin source express

A

gooseloid - cells far away express brachyury
theres are transcription factors which regulate distinct target genes leading to differentiation of specific mesodermal cell types

45
Q

what happens when the organiser O in a chick is transplanted

A

it induces a new embryonic axis with patterned mesoderm and a nervous system

46
Q

what do grafts of an organiser produce

A

an additional body axis which contains neural tissue and a mesoderm

47
Q

what happens when bification of the signalling centre in early development occurs

A

2 primitive streaks are formed leading to twins which are not always fully formed

Cell and Developmental biology (13 decks)

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