Models and Principles in Animal Development (2 lectures)

Question 1

7 eukaryotic model organisms

Answer 1

Mouse, chicken, xenopus, zebrafish, drosophila, c. elegans, yeast

Question 2

5 stages of vertebrate development

Answer 2

cleavage
blastula
gastrulation
neurulation
pharangula

Question 3

cleavage stage

Answer 3

early cell division, but no increase in cytoplasmic mass

Question 4

holoblastic cleavage

Answer 4

complete cleavage

Question 5

meroblastic cleavage

Answer 5

incomplete cleavage, e.g. cells dividing only on one side

Question 6

empty space in a cleaving embryo

Answer 6

blastocoel

Question 7

blastula stage

Answer 7

hollow stage

Question 8

gastrulation

Answer 8

germ layer formation, envagination of the mesoderm

Question 9

neurulation

Answer 9

formation of the neural plate, folding of the neural tube

Question 10

pharangula stage

Answer 10

post-anal tail, dorsal neural tube, segmentation- point at which vertebrate embryos tend to look very similar

Question 11

hourglass model of development

Answer 11

period of morphological constraint- basic body structure being laid out w hox genes

Question 12

xenopus pros and cons

Answer 12

pros
-easy to keep the adults
-external fertilisation, can get synchronised development of a bunch of embryos
-large embryos, easy to manipulate
cons
-slow to reach sexual maturity, annoying for genetics
-transgenics are difficult

Question 13

zebrafish pros and cons

Answer 13

pros
-easy to keep, they’re fairly chill
external fertilisation for synchronised development
transparent, so good for microscopy
-short generation times- good for genetics
cons
-duplicated genome makes things hard sometimes

Question 14

chicken pros and cons

Answer 14

pros
-eggs laid so easy to get to and manipulate
-windowing for easy access to the embryo
-good for grafting experiments
cons
-internal fertilisation, hard to access early stages
-embryos are dense
-long generation times, expensive to keep

Question 15

unusual aspects of mouse development

Answer 15

inside of the gastrula ends up on the outside of the embryo- ‘flipped’ stage
embryo needs to ‘turn’ itself at 8ish days old

Question 16

mice pros and cons

Answer 16

pros
-adults easy to keep in large numbers
-we know a lot about their genetics, so easy to do those kinds of experiments
-mammals, so more medically relevant
cons
-internal fertilisation and growth
-microscopy is a bit hard

Question 17

summary- considerations when picking a model organism

Answer 17

can adults be kept in the lab easily?
embryonic size and accessibility
what techniques can be applied- e.g. injection, grafting, culture
genetics?
phylogenetic position
does it have the right character

Question 18

cell fate

Answer 18

what a cell will, or has, become

Question 19

cell lineage

Answer 19

where a cell came from

Question 19

methods of tracking cell fate and lineage

Answer 19

photoconversion- activating a cell, and then following it
3D imaging- method of exactly tracing a lineage

Question 19

commitment

Answer 19

when cells are on a developmental path

Question 20

specification

Answer 20

reversible commitment

Question 21

determination

Answer 21

irreversible commitment

Question 22

differentiation

Answer 22

when specific functional cell types are formed (as inferred by morphology or transcriptional profiles)

Question 23

how would we test if cells are committed?

Answer 23

looking at if the cells behave the same in culture as they do in vivo- e.g. do they make limb cells in culture

Question 24

how can we tell if cells are specified or determined?

Answer 24

tranplantation- do cells fo what they do in the donor? this would make them determined

Question 25

what did Mangold do

Answer 25

transplantation experiments on newts, showing that you can determine the functionality of specific regions early on in the embryo

Question 26

what is an organiser region

Answer 26

region or group of cells which can both induce different fates of, and pattern, adjacent cells

Question 27

what is pattern formation

Answer 27

the step generally preceding morphological change- distinct spatial territories are specified by different molecular or transcriptional identities

Question 28

important model for determining positional identity

Answer 28

french flag model

Question 29

what is a GRN

Answer 29

gene regulatory network- often quite complex set of gene interactions which help set up regions of a developing organism

Question 30

key principles of the Turing reaction-differentiation model

Answer 30

-no external intervention
-patterns emerge at the global level from local interactions among smaller components
-idea of repression and activation systems- inhibitor which diffuses faster than the activator
-often get oscillatory patterns just from this inhibitor/activator pattern

Question 31

turing vs french flag models

Answer 31

french flag model focuses on how positional information can be determined by local morphogen gradient- turing model says this info doesn’t directly correlate w morphogen conc
turing model is a bit less about direct determination of positional information based exclusively on morphogen concentrations