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Genetics > Body Plans Development > Flashcards

Body Plans Development Flashcards

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Biology 101 flashcards
1
Q

What is morphogenesis

A

Process by which an organism or structure develops into a 3D form (like in embryogenesis)

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2
Q

Name the 3 axes of an embryo body plan

A

Antero posterior - head (anterior) to tail (posterior)

Dorso ventral - dorsal (back) to ventral (belly)

Left- right axis - 2 lateral sides of embryo

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3
Q

Where is the neural tube located

A

At the dorsal side (back)

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4
Q

What has to occur for body plans to develop

A

Cell distance into a blastocyst from an embryo

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5
Q

What 2 cells present in blastocysts

A

Trophoblast - cells for structure support

Embryoblast - cells that form embryo

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6
Q

What determines type of signalling and how readily it binds to receptors in cell signalling during development

A

Genes the embryo possesses

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7
Q

What are morphogens

A

Growth factors that control the position of cell types

They repress or induce gene expression depending on concentration

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8
Q

Give major examples of morphogens

A

SHH (hedgehog signal)

Wnt

RA (retanoic acid)

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9
Q

How does morphogens from source to sink change to induce different gene expression

A

Source = most morphogen and then it diffuses in lower conc. the lower conc areas might have different genes expressed

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10
Q

Which protein morphogen in flies is famous for activating transcription of ANTERIOR STRUCTURES

A

Bicoid protein

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11
Q

Which morphogen in flies opposes bicoid in antero posterior polarity by suppressing translation closer to ANTERIOR

A

Nanos

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12
Q

Why is diffusion of morphogens easier in flies

A

Due to it being one egg and not having to go through cellularised tissue

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13
Q

How do homeobox genes use morphogens to switch on genes at different areas

A

Morphogen concentration eg high could allow gene expression at anterior

At low conc it allows gene expression at posterior

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14
Q

Name the 4 ways morphogenic signals pass cellular tissues

A

1- restricted diffusion model

2- planar transcytosis model

3- lipoprotein transfer model

3- cytoneme model

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15
Q

Explain the restricted diffusion model of how morphogens can diffuse

A

They can bind to carbohydrates on the cell surface when secreted and diffuse along the surfaces of cells

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16
Q

Explain planar transcytosis

A

Morphogens pass directly via cytoplasm of cells across

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17
Q

Explain lipoprotein morphogen transfer

A

When secreted lipoproteins can bind and allow movement across cell surface down gradient

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18
Q

Explain cytoneme model of morphogen diffusion

A

Morphogens using cytonemes (cell extensions) to move long distances

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19
Q

Name the 2 sources of morphogens in embryo (where they are high in conc) and what they form

A

1- AVE: anterior visceral endoderm - morphogens used to produce anterior end

2- the NODE - patterns the whole of the embryo including the anterior in sync with AVE

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20
Q

How do the node and the anterior visceral endoderm (AVE) have large conc of morphogens

A

That’s where the cells that release them are located

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21
Q

What can disruption of sources such as the Node have on the embryo (give SHH as example)

A

Can affect body plan of the embryo due to no gene expression in areas

Eg if disruption to shh the embryo can develop with no eyes or tail

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22
Q

What side in left right axis formation undergoes cell signalling through morphogens

A

Left side

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23
Q

How is the node important for left right asymmetry

A

Node releases morphogens such as RA and SHH which are wafted to left side of body to activate gene expression to form eg organ tissues

24
Q

How are morphogens directed in left right axis formation

A

Cilia on node cells waft to left side to get more gene expression

25
Q

What are PITX homeobox genes for

A

Development of organs and skeletal muscle

26
Q

Which morphogen on the left side is activated by node morphogen release on left side

A

Nodal TGF morphogen

27
Q

What does nodal tgf morphogen do when activated by node morphogens on left side

A

Activate pitX genes which allow for organ development

28
Q

How does dosage of pitX allow for organ asymmetry in the body

A

Higher conc areas will have different genes meaning different organs formed to low conc areas

29
Q

What in left right axial formation prevents signalling morphogens on right side

A

SHH sonic hedgehog

30
Q

What would happen if nodal signalling was on the right side

A

Organs would be reversed

31
Q

What would happen if nodal signalling was on both sides

A

There would be 2 left sides (left isomerism)

32
Q

What would happen if nodal signalling happened on neither side of body

A

Right isomerism (2 right sides of the body)

33
Q

How were frogs manipulated to see the effects of left right axis formation and signalling in embryo

A

Frog was dissected and the part where the node was was taken out and transplanted into another frog

It was rotated by 180• and this showed organs reversed in the frog embryo

= shows structure and orientation is dependant on nodal signalling

34
Q

Which gene knockout meant that instead of asymmetrical lung lobes, mice had 2 left lobes (left isomerism)

A

Lefty 1 / SHH gene - important for left side cell signalling (stops signalling on right) as pitX was found on both sides of lungs when it was knocked out = left isomerism

35
Q

Which genes famously are related to antero posterior axial formation

A

Hox genes / homeobox genes - found laterally across the human body aswell as flies (head to tail)

36
Q

Name the 3 main morphogens which affect homeobox genes in anterior posterior axes

A

Wnt - specific to anterior gene expression

RA(retanoic acid) - mid brain gene expression

FGF - caudal / tail region

37
Q

What would happen if hox 6 genes where ribs are were expresssed at the tail for example eg due to disruption on morphogen signalling

A

Ribs would grow at the tail

38
Q

Which morphogen is in high conc at dorsal region (back)

A

Wnt

39
Q

Which morphogen is at the ventral region at high conc

A

SHH

40
Q

What does sHH and wnt polarity in dorsal ventral axial formation cause

A

Different genes expressed which specify different neurones in the brain

By activating different homeobox genes

41
Q

What is the proximal and distal axis in terms of limbs such as the arms

A

Proximal is shoulder

Distal is the digits

42
Q

What is the anterior and posterior axis in the limbs

A

Anterior is what makes pinky distinct from posterior thumb

43
Q

Apart from proximal and distal and posterior and anterior in limbs, what other 2 axis are there

A

Front or back of the hand which is distinct

Left or right hand axis

44
Q

Which morphogens are important in proximal and distal axis from shoulder to digits

A

RA and FGF

45
Q

Which place on the limb has the most RA and the least FGF

A

Most RA = shoulder

Least FGF = shoulder

(Most FGF in digits)

46
Q

What type of genes do RA and FGF in the limbs affect expression of

A

Hox genes in the limbs

47
Q

Which centre is important for outgrowth of the limbs

A

Apical ectodermal ridge (AER)

48
Q

What happens if the apical ectodermal ridge is removed or duplicated

A

If removed no limb is grown

If duplicated it causes limb duplication

49
Q

What doesn’t the apical ectodermal ridge determine

A

Which limb is grown

50
Q

What is the most important morphogen in limb outgrowth

A

FGF (highest in the digits)

51
Q

Which morphogen is important in anterior posterior axis of the limbs (pinky to thumb) patterning

A

SHH

52
Q

Where is shh highest and lowest in the anterior posterior of the limb

A

Highest in the anterior (pinky)

Lowest in the posterior (thumb)

53
Q

Which centre is SHH on at the posterior of the limb

A

Zone of polarising activity (zpa)

54
Q

How does thalidomide alter the expression of morphogens like FGF and SHH

A

By disrupting the apical ectodermal ridge

And zone of polarising activity (zpa)

55
Q

How else apart form disrupting the AER and ZPA does thalidomide disregulate SHH and FGF signalling

A

By degradation of the transcription factor called sall4

Genetics (19 decks)

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