Development biology

Question 1

What is pattern formation/ regional specification in development?

Answer 1

The process by which a spatial and temporal pattern of cellular activities is organised within the embryo so that a well-ordered structure develops
An early step is allocation to different germ layers

Question 2

What are the three germ layers?

Answer 2

Endoderm
Mesoderm
Ectoderm

Question 3

What morphogenesis occurs in development?

Answer 3

Differential proliferation
Change in cell shape and size 
Cell movement 
Cell fusion
Cell death 
Gastrulation moves the germ layers relative to one another

Question 4

Why is there little growth in early development?

Answer 4

Basic body plan is being established instead

Question 5

The zygote is totipotent, what does this mean?

Answer 5

Generates all the cell types of the body and extra-embryonic tissues

Question 6

What is differentiation?

Answer 6

Process of cells become structurally and functionally specialised, reflecting activation and maintenance of a particular pattern of gene expression

Question 7

What is cleavage?

Answer 7

Rapid, multiple rounds of mitotic cell division where the overall size of the embryo doesn’t increase
The developing embryo is called a blastula after cleavage is completed

Question 8

What does cleavage produce?

Answer 8

Cluster of blastomeres

Question 9

What is the morula and when does it form?

Answer 9

Early stage in post-fertilisation development when cells have rapidly mitotically divided to produce a solid mass of cells (12-15 cells)
3 days after fertilisation

Question 10

Post-morula, subsequential tangential cleavages produce one polarised and one non polarised daughter cell. Why?

Answer 10

Outer cells have distinct apical and basal surfaces
Non-polarised cells form inner cell mass
First differentiation event in mammalian embryonic development

Question 11

What does the inner cell mass give rise to?

Answer 11

The embryo proper, and some extra-embryonic structures

Question 12

What is the blastocoel?

Answer 12

Fluid-filled blastocyst cavity

Question 13

What does active transport of sodium ions lead to in the blastocoel?

Answer 13

Active transport of sodium ions leads to fluid accumulation in the blastocoel
As ion conc increases, water flows in by osmosis
This inflates blastocoel

Question 14

What is the trophectoderm?

Answer 14

Outer cell layer of blastocyst that develops as well as inner cell mass

Question 15

What is the trophoblast derived from?

Answer 15

Trophectoderm

Question 16

What does implantation require?

Answer 16

Interactions between trophoblast cells and uterine cells

Question 17

What do the trophoblast cells do to help with implantation?

Answer 17

Express integrin proteins, which interact with extracellular matrix proteins expressed by epithelial cells of the uterine mucosa
Integrin/ laminin interactions promote attachment
Integrin/ fibronectin interactions promote migration

Question 18

At implantation, what is the inner cell mass now called?

Answer 18

Embryoblast

Question 19

What does the embryoblast form?

Answer 19

Epiblast

Hypoblast

Question 20

What is the epiblast?

Answer 20

Columnar cells adjacent to newly formed amniotic cavity

Will form embryo proper

Question 21

What is the hypoblast?

Answer 21

Small cuboidal cells adjacent to the blastocyst cavity

Will form extra-embryonic structures that will connect to the mother’s circulation

Question 22

Where does the primitive streak form after 2 weeks and what is it?

Answer 22

Forms on surface of epiblast in the region that will become posterior of the embryo
First sign of anteroposterior axis

Question 23

What happens in gastrulation?

Answer 23

Gatrula forms from blastula

Epiblast cells migrate through the primitive streak to create 3 germ layers

Question 24

What happens during neurulation?

Answer 24

Ectoderm folds along its central axis to form the neural tube

Question 25

What does the paraxial mesoderm segment into and what do these generate?

Answer 25

Somites | generate trunk and limb muscles, dermis and vertebrae

Question 26

What does the endoderm give rise to?

Answer 26

Epithelial lining of gastrointestinal tract

Question 27

What happens during the embryonic period?

Answer 27

Germ layers give rise to tissues and organ systems (organogenesis) This is where most structural birth defects are induced

Question 28

What are the common stages most animals develop through?

Answer 28

``` Fertilisation Cleavage to form blastula Gastrulation to reorganise structure and generate germ layers Neurulation Organogenesis ```

Question 29

What are differentiated cells characterised by?

Answer 29

The proteins they contain

Question 30

What is genomic equivalence?

Answer 30

Almost all somatic cells have a complete copy of the genome

Question 31

What does VegT do?

Answer 31

VegT is a protein that binds DNA and actives expression of transcription factors that mediate endoderm differentiation and nodal TGFbeta signalling factors that are secreted and induce responding cells to form mesoderm

Question 32

How is development affected by blocking VegT gene function?

Answer 32

Removing VegT from the oocyte interferes with both endoderm development and mesoderm induction