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BMS109 Develpomental > Making a Limb Bud > Flashcards

Making a Limb Bud Flashcards

1
Q

What day is the body plan established in chicks

A

day 2

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2
Q

Describe the body plan of a homozygous hox5b knockout mouse

A

forelimbs develop at more anterior level

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3
Q

What do hox genes restrict

A

expression of fibroblast growth factors

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4
Q

What are fibroblast growth factors required for

A

limb bud outgrowth

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5
Q

What do hox genes control

A

where FGF is expressed

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6
Q

What are FGFs

A

secreted signalling molecules

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7
Q

What happens to homozygous knockout mice of FGFs

A

embryos lack limb buds

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8
Q

What is the function of FGFs

A

sufficient and required for limb bud formation

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9
Q

Describe the effect of a local application of FGF to a chick

A

Forms an ectopic limb bud which expresses sonic hedgehog

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10
Q

Describe the apical ectodermal ridge in chicks

A

rigid ridge of thickened epithelium around lip of limb bud

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11
Q

What is the function of the apical ectodermal ridge

A

maintains progress zone, important in developing limb

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12
Q

What does removal of the apical ectodermal ridge cause

A

truncation of the limb - but some patterning still continues

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13
Q

What does the apical ectodermal ridge secrete

A

signalling molecules

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14
Q

What can substitute for the AER

A

FGFs - which restore near normal growth

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15
Q

Where is the progress zone located

A

most distal region of limb bud

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16
Q

what are the cells in the progress zone derived from

A

mesoderm

17
Q

Describe the cells in the progress zone

A

undifferentiated rapidly dividing cells

18
Q

What does the length of time the cells stay in the progress zone determine

A

cell fate along the proximal-distal axis

19
Q

What experiment tests the role of the progress zone

A

heterochronic graft

20
Q

Describe the zone of polarising activity

A

region of posterior limb bud mesenchyme

21
Q

What is the effect of transplanting the ZPA underneath anterior AER

A

induces symmetrical duplications of limb about the AP axis

22
Q

What does the ZPA form

A

AP axis of limb

23
Q

Where is sonic hedgehog mRNA expressed

A

Zone of polarising activity

24
Q

What happens when sonic hedgehog mRNA is translated

A

influences pattern across whole limb bud

25
Q

what is shh

A

morphogen

26
Q

Is shh necessary or sufficient to pattern axis of limb

A

sufficient

27
Q

Describe the expression of shh

A

very localised to ZPA

28
Q

Which region of the limb bud acts as an organising centre

A

ZPA

29
Q

What type of signal is shh

A

long range signal

30
Q

What is needed for the formation of digits

A

apoptosis, programmed cell death, differential growth & proliferation

31
Q

What germ layer determines the pattern of cell death

A

mesoderm

BMS109 Develpomental (13 decks)

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