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Cells to Organisms - Lectures > Lecture 16. Organising a Body Plan in Multicellular Organisms > Flashcards

Lecture 16. Organising a Body Plan in Multicellular Organisms Flashcards

1
Q

What can give rise to complex multicellular organism ?

A

A fertilised egg cell

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2
Q

How do most multicellular organisms arise ?

A

Sexual reproduction

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3
Q

What does sexual reproduction ensure ?

A

Genetic variation and adaptability in the population

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4
Q

How is a diploid individual formed ?

A

Two haploid gametes produced by parents fuse

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5
Q

What process takes places in the production of gametes ?

A

Meoisis

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6
Q

What does meiosis achieve ?

A

Halving of the genetic material

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7
Q

What is gametogenesis ?

A

Produces a haploid sperm and egg

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8
Q

What are the two functions of fertilisation ?

A
  1. Brings haploid gametes together to form the new individual
  2. Activates the developmental processes in the egg
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9
Q

How are different cell types produced ?

A

Progressively as the embryo develops

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10
Q

What is special about a fertilised egg cell ?

A

It is the only cell that naturally has the capacity to form a new unique individual

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11
Q

What are model organisms use for ?

A

Researchers study development in model organisms to identify general principles

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12
Q

What are some examples of invertebrate model organisms ?

A
  1. Drosphilia melanogaster
  2. Caenorhabditis elegans
  3. Echinodermata
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13
Q

What are some examples of vertebrate model organisms ?

A
  1. Xenopus laevis - frog
  2. Gallus - chick
  3. Mus musculus - mouse
  4. Danio rerio - zebrafish
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14
Q

What is an example of a plant model organism ?

A

Arabidopsis thaliana

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15
Q

What are the steps involved in building a new organism ?

A
  1. Fertilisation
  2. Cleavage
  3. Gastrulation
  4. Neurulation
  5. Organogenesis
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16
Q

What does cleavage form ?

A

A hollow ball or disk of cell eg. blastula, blastoderm

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17
Q

What is gastrulation ?

A

Turns the blastula into a three germed layer

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18
Q

What is neurulation ?

A

A special type of organogenesis - it sets cells as and forms the entire nervous system

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19
Q

What does a three layered embryo have ?

A

A primitive gut called a gastrula

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20
Q

What are the three germ layers called ?

A

Ectoderm, mesoderm, endoderm

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21
Q

Where is the ectoderm ?

A

Outer layer

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22
Q

Where is the mesoderm ?

A

Middle layer

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23
Q

Where is the endoderm ?

A

Inside layer

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24
Q

What does gastrulation lead to ?

A

The generation of germ layers placed in the correct relative positions in the embryo

25
Q

What does gastrulation result in ?

A
  1. Elaborate cell movement
  2. Differentiation of cells into three types
  3. Positioning of cell layers in the gastrula which allows them to interact in new ways
  4. Communication between cells that are now different to one another
26
Q

What is the first operational organ system in the developing embryo ?

A

The circulatory system

27
Q

What are the three major inter-related processes involved in building a complex organism from a single fertilised egg cell ?

A
  1. Cell division
  2. Cell differentiation
  3. Morphogenesis
28
Q

What is the basis of cellular differentiation ?

A

Differential gene expression

29
Q

What is the turn on and turn off genes in specific cells controlled by ?

A

Cell specific transcription factors that bind to gene specific enhancer regulatory elements

30
Q

What is morphogenesis ?

A

The emergence of shape and structure in the body plan of the developing embryo

31
Q

How do we define position in a 3D object ?

A

By co-ordinates along 3 axes

32
Q

How do cells receive information about their relative position ?

A
  1. Localisation of cytoplasmic determinants

2. Induction

33
Q

What is induction ?

A

Where one group of cells influences the development of a neighboring group of cells

34
Q

How is induction achieved at a molecular level ?

A

Through cell signaling

35
Q

How can genes be turned on and off ?

A

In response to signals that a cell receives

36
Q

What is meant by competence ?

A

The ability to respond to a signal

37
Q

What do maternal effect genes do ?

A

Establish poles and axes

38
Q

What do segmentation genes do ?

A

Divide the body into segmental units

39
Q

What happens in mutants of homeotic genes ?

A

Structure characteristic of a particular part of the animal arise in the wrong place

40
Q

What does Antennapedia mutant do ?

A

Leads to the formation of legs at the site of antenna

41
Q

What are transcription factors ?

A

Master genes that guide developmental events

42
Q

What are hox genes ?

A

A special set of such genes that encode transcription factors, they are the genes mutated in homeotic mutants. They control the identity of body parts

43
Q

What is the vertebrate limb a good model for ?

A

How positional information is organised leading to morphogenesis

44
Q

What are some points about the vertebrate limb ?

A
  1. Formed relatively late in development
  2. External position
  3. Obvious 3D pattern
45
Q

What are secondary fields ?

A

Regions of the embryo that emerge or are defined after the primary body plan is laid down

46
Q

What has to be established to pattern the secondary field ?

A

A new set of positional cues

47
Q

What marks out the future skeleton of the limb ?

A

Cartilage condenses with the mesenchyme

48
Q

How does cartilage form bone ?

A

It ossifies

49
Q

What is an organiser ?

A

A group of cells that influences the development of surrounding tissue

50
Q

How is the organiser function achieved ?

A

Induction

51
Q

What are the two important organisers in the limb ?

A
  1. The apical ectodermal ridge

2. The zone of polarising activity

52
Q

What happens if the apical ectodermal ridge is removed ?

A

The limb ceases to grow

53
Q

What does the removal of the apical ectodermal ridge at different stages lead to ?

A

The trunification of the limb at the different points along the p/d axis

54
Q

Where is the zone of polarising activity located ?

A

In the posterior mesoderm of the developing limb bud

55
Q

What happens when the zone of polarising activity is transplanted to the anterior ?

A

It induces a duplication of the A/P pattern of digits, a mirror image of the normal digits

56
Q

What was the zone of polarising activity shown to be ?

A

A dose dependent phenomenon since transplantation of only some cells lead to partial duplication

57
Q

What lies downstream of p/d and a/p signaling in limb patterning ?

A

Hox genes

58
Q

What is produced by the zone polarising activity to pattern along the a/p axis ?

A

A classic morphogen

Cells to Organisms - Lectures (36 decks)

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