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Genetics and evolution > Developmental biology! > Flashcards

Developmental biology! Flashcards

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1
Q

What are the key processes in development?

A

Cell division, Pattern formation, Morphogenesis, Growth, Differentiation

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2
Q

What is cleavage in development?

A

Rapid cell division without growth producing blastomeres, leading to the morula and then the blastocyst.

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3
Q

What happens during compaction of the morula?

A

Increased cell-cell adhesion forms a compact ball of cells via tight junctions; establishes apical-basal polarity.

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4
Q

What is the first cell fate decision in the mammalian embryo?

A

Segregation into trophectoderm (placenta) and inner cell mass (embryo proper).

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5
Q

How does the blastocoel cavity form?

A

Na+ transport into the cavity draws water by osmosis, inflating the cavity due to hydrostatic pressure.

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6
Q

What is the role of the zona pellucida?

A

Prevents premature implantation in the oviduct.

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7
Q

How does implantation occur?

A

Trophoblast integrins interact with laminin and fibronectin of uterine epithelial cells.

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8
Q

What are the two layers of the embryoblast and their fates?

A

Epiblast forms the embryo proper; Hypoblast forms extra-embryonic tissues.

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9
Q

What is the primitive streak?

A

A structure marking the start of the anteroposterior axis; site of epiblast cell migration during gastrulation.

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10
Q

What are the three germ layers formed during gastrulation?

A

Ectoderm (skin, nervous system), Mesoderm (muscle, bone, blood), Endoderm (gut lining, lungs, liver, pancreas).

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11
Q

What is neurulation?

A

Folding of ectoderm to form the neural tube, which becomes the CNS.

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12
Q

What structures do somites give rise to?

A

Muscles, vertebrae, and dermis of trunk and limbs.

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13
Q

What does the endoderm form?

A

GI tract lining, liver, pancreas, respiratory tract.

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14
Q

What is organogenesis?

A

Weeks 3–8; germ layers form tissues and organs; period most sensitive to birth defects.

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15
Q

What is genomic equivalence?

A

All somatic cells contain the same DNA - have a complete copy of the genome; demonstrated by somatic cell nuclear transfer (SCNT).

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16
Q

How is gene expression regulated during development?

A

By cytoplasmic determinants and inductive signals.

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17
Q

What are cytoplasmic determinants?

A

Molecules like transcription factors that influence cell fate through uneven distribution E.g. body axis etc.

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18
Q

What are inductive signals?

A

Cell-cell interactions or diffusible factors that influence the fate of nearby cells.

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19
Q

What are examples of model organisms in developmental biology?

A

Xenopus, zebrafish, mouse, fruit fly, chick, C. elegans.

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20
Q

What is the role of VegT in Xenopus?

A

Transcription factor at vegetal pole; activates genes for endoderm and Nodal signalling.

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21
Q

How is VegT function studied?

A

Loss-of-function blocks endoderm/mesoderm; gain-of-function induces endoderm genes in ectoderm.

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22
Q

What is Wnt signalling and its developmental role?

A

Activates β-catenin, which enters nucleus to activate dorsal genes; inactivation of GSK-3β allows β-catenin stabilization.
Wnt binds, inactivates GSK-3B, allows B-catenin to enter nucleus, which turns on transcription factors

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23
Q

What triggers dorsal identity in Xenopus?

A

Cortical rotation redistributes Wnt11 and GSK-3-binding protein to inhibit GSK3-B, therefore allowing the action of β-catenin dorsally, meaning the Wnt pathway is activated on the dorsal side of the embryo

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24
Q

How does β-catenin influence development?

A

Activates siamois and goosecoid to initiate organiser and dorsal structure development. Gives rise to the dorsal ventral divide

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25
How does the organiser function?
Secretes signals to pattern mesoderm and neuralise ectoderm; can induce a secondary axis. Basically sorts out body plans
26
What is positional information?
Signals tell cells where they are; cells respond by expressing specific transcription factors.
27
How is skeletal muscle differentiation controlled?
MyoD is a master regulator induced by signals to activate muscle-specific genes.
28
What can MyoD do if overexpressed?
Convert fibroblasts into muscle cells; acts as a master switch.
29
What ensures proper differentiation?
Combinations of transcription factors controlled by cytoplasmic inheritance and intercellular signals.
30
What is the blastocoel?
Fluid-filled blastocyst cavity
31
What is genomic equivalence?
All somatic cells have the same genome, shown by somatic cell nuclear transfer (SCNT).
32
What experiment proves genomic equivalence?
SCNT experiments where a nucleus from a differentiated cell directs the development of a new organism.
33
What causes cells to become different during cleavage?
Asymmetric partitioning of cytoplasmic determinants such as transcription factors.
34
How do inductive signals influence cell fate?
They trigger specific gene expression patterns in responding cells.
35
What is the role of cytoplasmic determinants in early development?
They establish initial asymmetries and influence gene expression.
36
What do cytoplasmic determinants help specify in C. elegans?
The germ line, through segregation of P-granules.
37
Name five common model organisms for developmental biology.
Mouse, frog (Xenopus), zebrafish, fruit fly (Drosophila), nematode (C. elegans), chick.
38
Where is VegT mRNA localised in Xenopus eggs?
At the vegetal pole.
39
What does VegT regulate?
Endoderm development and mesoderm induction via transcription factor and Nodal expression.
40
What are the three criteria for proving a molecule's role in development?
It must be expressed at the right time and place, be necessary, and be sufficient.
41
What happens if VegT is removed from Xenopus oocytes?
Endoderm development and mesoderm induction are disrupted.
42
What does ectopic VegT expression in ectoderm cause?
Expression of endoderm-specific genes.
43
What does Wnt signalling do?
It stabilises β-catenin, allowing it to enter the nucleus and activate target genes.
44
How is β-catenin normally regulated?
Destroyed by GSK-3 unless Wnt signalling inhibits this destruction.
45
What does sperm entry trigger in the egg?
Cortical rotation, redistributing Wnt pathway components.
46
Where does β-catenin accumulate?
In the nuclei on the future dorsal side of the embryo.
47
What genes does β-catenin activate?
Transcription factors such as siamois and goosecoid.
48
How does the dorsal mesoderm (organiser) form?
High Nodal + β-catenin induces organiser; low Nodal induces ventral mesoderm.
49
What is the role of the organiser in development?
It secretes signals that pattern mesoderm and induce neural tissue.
50
What experiment demonstrates organiser function?
Grafting organiser tissue to the ventral side induces a secondary body axis.
51
How is cell fate determined during differentiation?
By the signals cells receive and the combination of transcription factors they express.
52
What does MyoD do?
It is a master regulatory gene that induces skeletal muscle differentiation.
53
How do MyoD-expressing cells become muscle?
MyoD activates muscle-specific genes and causes cells to differentiate into myoblasts and myotubes.
54
What happens if MyoD is overexpressed in non-muscle cells?
They can be reprogrammed to form muscle cells.
55
Why must master regulators like MyoD be tightly controlled?
To prevent inappropriate or ectopic differentiation.
56
What patterns the germ layers in early development?
Cytoplasmic determinants and inductive signalling.
57
How do transcription factors drive differentiation?
They regulate tissue-specific gene expression in response to signals.
58
What is cell lineage?
The developmental history of a cell traced from the original fertilised egg.
59
What are the main molecules involved in early patterning?
VegT (TF), Nodal (TGF-β), Wnt11 (signalling), β-catenin (TF), GSK-3β (kinase), Siamois & Goosecoid (TFs), MyoD (TF).
60
What does gastrulation do?
Moves the germ layers relative to one another
61
What is morphogenesis?
Creation of structure and form
62
What is the nervous system derived from?
Ectoderm
63
What is the heart derived from?
Mesoderm
64
What level of potency is the zygote?
Totipotent - then progressive cell commitment occurs, so early embryo is pluripotent and so on.
65
What do the non-polarised cells that form from the morula create?
The inner cell mass
66
What do the outer cells of the morula create?
Trophectoderm
67
What are the 5 parts of the embryo at day 5?
1. Zona pellucida 2. Trophoblast (derived from trophectoderm) 3. Hypoblast (part of inner cell mass) 4. Blastocyst cavity 5. Epiblast (part of inner cell mass)
68
What kind of cells form the 3 germ layers upon invagination into the primitive streak?
Epiblast cells
69
What structure segments into somites after neurolation?
paraxial mesoderm
70
What are the 5 common stages most animal development proceeds through?
- fertilisation * cleavage to form the blastula * gastrulation to reorganise the structure of the embryo and generate the germ layers * neurulation * organogenesis
71
Asymmetrically segregated cytoplasmic determinants specify the germ line in what?
C. elegans
72
What is VegT?
VegT is a maternally deposited mRNA encoding a T-box transcription factor. It's present in the vegetal pole of the Xenopus egg (hence the name VegT)
73
What is cortical rotation?
Cortical rotation is a movement that happens after fertilisation, when the outer layer (the cortex) of the egg rotates ~30° relative to the inner cytoplasm. Triggered by sperm entry Direction of rotation is toward the sperm entry point The future dorsal side of the embryo forms opposite the point of sperm entry
74
What happens during cortical rotation?
The rotation redistributes dorsalising factors (like Wnt11 and GSK-3-binding protein) from the vegetal pole to one side of the egg. These determinants accumulate on the dorsal side, where they activate the Wnt/β-catenin pathway
75
Does sperm entry end up being dorsal or ventral?
Ventral
76
What cells produce MyoD?
Myoblasts
77
These are the molecules you need to know babygirls
| **Molecule** | **Type of molecule** | **Function (where and what)** |

Genetics and evolution (16 decks)

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