3: L12

Question 1

3 Main events of development

Answer 1

Cleavage
Gastrulation
Organogeneisis

Question 2

2 main principals in cleavage

Answer 2

cell division

pattern formation

Question 3

main principal in Gastrulation

Answer 3

morphogenesis

Question 4

2 main principal in Organogeneisis

Answer 4

Cell differentiation

growth

Question 5

As cleavage proceeds what are 3 stages of the cell ball names

Answer 5

oocyte > morula >blastula

Question 6

what are the factors that increase and decrease with cleavage proceed

Answer 6

decrease cell division
decrease maternal determinants
inc embryonic gene expression

Question 7

What is change of plane in cleavage influenced by

Answer 7

by yolk amount
o High – Vegetal pole
o Low – Animal Pole
o Mammals - +/- yolk free (don’t see change in plane as much) - placenta

Question 8

describe 2 processes of cleavage pattern formation

Answer 8

• Localisation of cytoplasmic factors (specific mRNAs & proteins) used as morphogenetic information to lay blueprint for body plan
o (body axis formation)
• Maternal vs zygotic factors A-P & V-D
o Determines spatial and temporal distribution

Question 9

what is gastrulation- morphogenesis

Answer 9

formation of 3 germ layers (mesoderm, ectoderm, endoderm)

Question 10

do zygotic gene expression inc or decrease when cleavage ends

Answer 10

inc

Question 11

how does blastula rearrange into 3 layers

Answer 11

internalisation and 2. migration

Question 12

what do ecto, meso and endo turn into

Answer 12

ecto- skin + NS
Meso- most organs
endo- linings of digestive and respiratory

Question 13

what is gastrulation dependent on

Answer 13

organizers

Question 14

what does an organiser do

Answer 14

• Responsible for initiating and coordinating specific differentiation patterns, but also in a temporal and special way, driving this process of moving cells from one region to another to set up these three layers

Question 15

what are organisers called in mammals and birds

Answer 15

o Mammals= Spemann organizer

o Bird: Hensens node

Question 16

what determines location of organiser

Answer 16

• Sperm entry

Question 17

what are autonomous and cell conditioning signals in organizer function

Answer 17

Autonomous’ signals: zygotic transcription factors (influence own environment) or
2. Cell conditioning signals: zygotic secretion factors (diffuse away from cell and influence other cells)

Question 18

what are vegetable animal and marginal cells turn into

Answer 18

• Vegetal= endodermal cells
• Animal= epidermal
• Marginal= mesoderm

Question 19

what is morphogen

Answer 19

a signal molecule that imposes a pattern on a field of cell

i.e. concentration gradient

Question 20

3 axis of developmetn

Answer 20

A-V animal veg
(internal/external)
AP anterior posture (head + tail)
DV dorsoventral (back and belly)

Question 21

describe neurulation in organogenesis

Answer 21

• Neural tube + below it = gives signals to give instructions to cells to become dorsal/ventral/lateral

Question 22

Where does the CNS come from and how

Answer 22

• CNS comes from neural plate(at cranial region towards causal) via signals such as inhibition of bone morphogenetic protein (BMP) signalling

1. Within neuro ecto derm region, BMP production inhibition initiates migration and division= produces neural folds (which fuse together)
2. Production of ventralising signals (via sonic hedgehog on neural plate location where vaginisation is occuring= together forms neural tube
3. Invagination complete + ecotderm plate seals itself up again
4. Proteins maintain dorsal and ventral polarity // continue secrete factors (allows PNS)

Question 23

what process gives rise to fingers

Answer 23

apoptosis

Question 24

Describe organogenesis example brain compartmentalisation

Answer 24

(defines boundary between mid-and hindbrain)
• Some inhibitory and promotion factors drive process + gives rise to distinct neural tissue
o Differential expression allows process to proceed
o Movement= formation of Forebrain, Midbrain, hindbrain
• Process continues= Further 3d structure form