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Cell Bio & Developmental Genetics > Lecture 6 (3a) Gastrulation > Flashcards

Lecture 6 (3a) Gastrulation Flashcards

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Biology 101 flashcards
1
Q

Cleavage

A

rapid mitotic divisions
- in Drosophila, only nucleus
• After cleavage = blastula
- blastoderm in Drosophila

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2
Q

Gastrulation

A

transforming a hollow ball into a 3-layered structure

• INVAGINATION TO FORM LAYERS

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3
Q

Germ layer

A

main division into cell types

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4
Q

Evtoderm makes

A

skin and nervous system

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5
Q

Mesoderm and endoderm make

A

inner structures

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6
Q

Organogenesis

A

different tissues and organs from

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7
Q

Metamorphosis

A

larval stage to maturity

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8
Q

The life of a new frog begins with the

A

fusion of the genetic material of the sperm and egg

fertilization

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9
Q

After fertilization

A

female frog lays eggs

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10
Q

Animal cap

brown part

A

• ectoderm in blastula
• remove = form epidermis
= some intrinsic factors that specify genes
• take from different regions - they sort themselves, reconstruct themselves

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11
Q

The first process after fertilization

A

CLEAVAGE

eg 2-cell embryo to 8-cell embryo

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12
Q

Somite

A

lateral mesoderm to spinal cord forms muscles and vertebrae

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13
Q

Cleavage results in formation of the

A

blastula

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14
Q

The blastula is a

A

hollow ball

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15
Q

Cavity in the blastula is called a

A

blastocell

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16
Q

Gastrulation begins with the formation of a

A

slit in the future dorsal side of the embryo

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17
Q

After gastrulation

A

organs and tissues are formed

• eg neural groove (to become neural tube)

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18
Q

The cells that generate the 3 germ layers are

A

present in the late blastula

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19
Q

Mid-blastula transition

A
  • shortly before gastrulation

* transcription is activated in the embryo

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20
Q

Both endoderm and ectoderm are specified by

A

maternal cell fate determinants
• animal half expresses maternal factor ENDODERMIN
+ zygotic factor FOX1E
• vegetal half expresses maternal factor VEGT
+zygotic factor NODAL (mesodermal induction)

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21
Q

Explants from animal cap form

A

ectodermal derivatives

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22
Q

Explants from vegetal cells form

A

endodermal derivatives

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23
Q

Explants from animal cap and vegetal cells form ectoderm and endoderm derivatives

A

AUTONOMOUSLY

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24
Q

Germ layer cells reconstruct their spatial relationship

A

after dissociation

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25
Q

In Xenopus, endoderm development is initiated by the maternal transcription factors

A

VegT and Veg1

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26
Q

VegT and Veg1 found in

A

endoderm

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27
Q

One maternal factor activates a cascade of

A

embryonic genes

VEGT ACTIVATES THE EXPRESSION OF MANY ZYGOTIC TRANSCRIPTION FACTORS

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28
Q

These transcription factors factors regulate each other and there expression is maintained by

A

Nodal

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29
Q

Nodal

A
  • activated by VegT

* is a morphogen, especially in future dorsal and lower concentration to ventral

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30
Q

Nodal is a morphogen and accumulates in the

A

endoderm

31
Q

Mesoderm

A

induced by Nodal and at same time told what type of mesoderm it is to form

32
Q

Morphogen

A

proteins in concentration gradient
• cells respond to different concentrations
• instruct cells to adopt different cell fates at different concentrations

33
Q

The nodal gradient determines

A

the type of mesoderm formed

34
Q

Xnr is highest in

A

the dorsasl region

35
Q

The various mesodermal fates are specified by

A

the Xnr gradient

36
Q

Nodal is activated by

A 
β-catenin + VegT + Vg1 
--> gradient
--> different mesodermal cells
• organizer of dorsal structure
-- gradient ventral to dorsal
37
Q

Additional factors required for mesdoerm induction:

A

VegT also activates the secreted factors activin and Derriere which in turn induce the formation of mesoderm by activating brachyury

38
Q

Brachyury is expressed in

A

all mesodermal cells

39
Q

In the late blastula, the cell fates of

A

the cell within the individual germ layers are determined

• additional signalling pathways such as Wnt and FGF are required for regional specification of the germ layers

40
Q

Cells are made different

A

with different morphogens in different concnetration

41
Q

Cell fates are determined in

A

the late blastula stage

42
Q

The fate map varies in different vertebrae groups because

A

the cleavage pattern is different

43
Q

Internalization of the endoderm and mesoderm occurs at

A

a dorsal area - the BLASTOPORE

44
Q

Internalization is shown as a

A

slit (meso and endo)

45
Q

Mesodermal and endodermal cells migrate towards the

A

animal pole

46
Q

The ectoderm expands towards the

A

vegetal pole

47
Q

Gastrulation varies in different groups but

A

the result is the same
• ectoderm
• mesoderm
• endoderm

48
Q

Gastrulation in the human embryo

A

endoderm and mesoderm are internalized through the primitive groove

49
Q

Epiblast

A

human embryo
• disc-like
• internalized at groove (meso and endo)

50
Q

Formation of the germ layers in Drosophila melanogaster

A
  • endoderm makes the midgut at poles

* the ectoderm forms the foregut and hindgut

51
Q

In Drosophila the mesoderm is

A

ventral

• the endoderm is split into an anterior and posterior region

52
Q

Germ cells are

A

NOT from germ layers
• germ cells are set aside before
(eg pole cells in Drosophila)

53
Q

The mesoderm is

A

internalized

54
Q

In vertebrates, the mesoderm forms

A

the muscles among others

55
Q

At the same time as the mesoderm is internalized, the endoderm

A

invaginatese anteriorly and posteriorly

56
Q

The endoderm forms the

A

midgut

foregut and hindgut are formed by the ectoderm

57
Q

The midgut is subdivided into

A

4 chambers

58
Q

The 3 germ layers give rise to

A

different organs and tissues

• the germ cells don’t arise from the 3 germ layers

59
Q

The notochord

A

induction of the nerve cord

• transient, forms mesoderm

60
Q

Derivatives of the somites

A
  • cartilage of vertebrae and ribs
  • muscles of the rib cage, limbs, abdominla wall back, tongue
  • tendons that connect the muscles to the bones
  • dermis of the dorsal skin
  • vascular cells of aorta and intervertebral blood vessels
61
Q

Functions of the mesoderm

A
  1. induces the mesodermal germ layer
  2. induces the formation of several mesodermal organs (notochord, heart, blood vessels)
  3. constructs the linings of 2 tubes within the vertebrate body - the digestive tube and the respiratory tube
62
Q

The endoderm induces the formation of

A

several mesodermal organs
(notochord, heart, blood vessels)

Anterior endoderm BMP signalling
–> cardiogenic mesoder (heart)
&
–> hemangiogenic mesoderm (blood, blood vessels)

63
Q

How is the gut endoderm regionally specified?

A

The areas of the digestive system are specified by regional transcription factors even before the endoderm forms a tube
• mesoderm instrutus the endoderm to different things
• boundaries in digestive system

64
Q

BMP signalling

A

tells cells what to do

65
Q

The stabilization of the boundaries results from

A

interactions with the mesoderm
• BMPs activate wnt signalling in intestine
• wnt inhibitors repress wnt signalling in stomach

66
Q

Wnt

A

wingless in drosophila
• for boundaries
(engrailed for posterior border)

67
Q

How are different areas initally specified in the endoderm?

A

• Shh gradient
• different Hox genes are expressed in response to different levels of Shh
• the mesoderm and endoderm “talk” back & forth
- induction both ways

68
Q

Cleavage of the egg shell results in the formation of the

A

blastula

69
Q

The cells that generate the 3 germ layers are present in the

A

late blastula

70
Q

The 3 germ layers are separated during

A

gastrulation
• endoderm
• mesoderm
• ectoderm

71
Q

The endoderm is specified by the maternal transcription factor

A

VegT

72
Q

The endoderm induces the

A

mesoderm and some of its derivatives

73
Q

The endoderm generates the

A

digestive and respirative tubes

Cell Bio & Developmental Genetics (27 decks)

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