Developmental Biology: Exam 2

Front 1

What drives gastrulation?

Back 1

Morphogenesis

Front 2

What is morphogenesis characterized by?

Back 2

Changes at the cell level

Front 3

What changes occur during morphogenesis?

Back 3

Cell adhesion (or the cell's affinities for each other)

Cell shape

Cell position (within embryo)

Front 4

What changes occur during gastrulation?

Back 4

Tissues are produced

Germ layers are determined and regionalized

The axes of the organism are detertmined

Front 5

What happens prior to gastrulation?

Back 5

The midblastula transition occurs.

Front 6

What changes occur during the midblastula transition?

Back 6

1. There is a change in the frequency of cell division. Cells acquire a gap/growth phase.

2. There is a change in gene expression known as the maternal-zygotic transition.

Front 7

When does the maternal-zygotic transition occur and what changes take place during it?

Back 7

It occurs prior to gasrulation.

The embryo takes over driving its own transcription (zygotic gene expression)

And the maternal determinants are no longer used.

Front 8

Who was Johannes Holtfreter and why is he important?

Back 8

He was a German embryologist.

Who...

Developed numerous cell-culture techniques,

Studied axes specification in the frog,

Studied neural development, and

Studied cell-cell interactions during gastrulation.

Front 9

What was tested and discovered in the Holtfreter and Townes experiments?

Back 9

Used post-gastrulation amphibian embryos.

Dissociation and regression of tissues:

1. Separated and recombined ectoderm and endoderm. Cells had a high affinity for cells of the same type and repelled each other.

2.Dissociated and reaggregated two ectodermal derivatives: epidermal and neural cells. Found that neural cells had a higher affinity for each other than did epidermal cells. Both cell types also had a positive affinity for each other.

Variety of Germ Layer Recombinations

Strongest affinity to weakest affinity:

neural ectoderm, mesoderm, endoderm, epidermal ectoderm

Front 10

Generalizations about tissues from Holtfreter and Townes experiments

Back 10

There exist strong affinities between cells within a tissue.

The weakest interfaces exist between cells of different tissues.

Front 11

Why is Malcolm Steinberg important?

Back 11

He examined the cell affinities for a variety of adult tissues, and found that these tissues sorted in relation to each other

Created the differential adhesion hypothesis.

Front 12

Differential adhesion hypothesis

Back 12

Different cell types have different adhesion properties

Cells will sort according to their strength of adhesion

They will organize themselves in such a way as to achieve the greatest thermodynamic stability

Front 13

What determines cell affinities?

Back 13

Cell adhesion molecules (CAMs)

Front 14

What 2 properties of cell adhesion molecules (CAMs) contribute to the affinities between cells?

Back 14

Qualitative properties: Different cells have different CAMs

Quantitative properties: The number of a single type of CAM on a cell as well as the number of types of CAMs on a cell

Front 15

What structures help alter the cytoskeleton

Back 15

Microfilaments

Front 16

What do microfilaments do to help alter the cytoskeleton

Back 16

Cleave cells by acting as a contractile ring

Change cell shape through apical constriction via a contractile actin network

Migrate a single cell by creating lamellipodium via actin/myosin bundles

Front 17

Types of morphogenic movement

Back 17

1. Invagination

2. Involution

3. Ingression

4. Delamination

5. Intercalation

6. Epiboly

Front 18

Describe invagination

Back 18

an in-pocketing

creates a sheath

invaginating cells undergo apical constriction

Front 19

Describe involution

Back 19

cells spiral under

Front 20

Describe ingression

Back 20

Single cells undergo epithelial to mesenchyme transition or mesenchyme to epithelial transition.

Cells sort of drip into new tissue

Front 21

Describe delamination

Back 21

Epithelial to mesenchyme and mesenchyme to epithelial transitions, one after the other. Creates 2 layers of tissue.

Front 22

Describe intercalations

Back 22

Multiple planes of epithelium merge to create a single plane

Front 23

Describe radial intercalation

Back 23

cell planes on top of each other

merge vertically to create one plane

Front 24

Describe medio-lateral intercalation / convergent extension

Back 24

cell planes next to each other

merge laterally to create one line of cells

elongate tissue in a line

Front 25

Describe epiboly

Back 25

Cells spreading

One of 3 ways:

radial intercalation

thinning of cells

proliferation

Front 26

Steps of gastrulation in sea urchins

Back 26

1. Ingression of primary mesenchyme

2. Invagination of endoderm

3a. Ingression of secondary mesenchyme

3b. Elongation of gut rudiment

4. Mouth formation

5. Differentiation of tissues

Front 27

What happens during ingression of primary mesenchyme in sea urchin gastrulation?

Back 27

The mesoderm ingresses

The primary mesenchyme will migrate to the vegetal and lateral regions of the blastocoel

Produce filopodia to detect their environment

Front 28

What happens during invagination of endoderm in sea urchin gastrulation?

Back 28

the endoderm invaginates to form the gut rudiment

Front 29

What happens during ingression of secondary mesenchyme in sea urchin gastrulation?

Back 29

Mesoderm

Ingresses off the end of the gut rudiment

Front 30

What happens during elongation of the gut rudiment in sea urchin gastrulation?

Back 30

The gut rudiment narrows and elongates via convergent extension of secondary mesenchyme. Filopodia act as anchors; they generate tension that drives elongation.

Front 31

What happens during mouth formation in sea urchin gastrulation?

Back 31

Secondary mesenchyme drags the gut to the lateral margins

The gut fuses with the lateral wall

(The sea urchin is a deuterostome; the invagination from the blastocoel forms the anus)

Front 32

What happens during the differentiation of tissues in sea urchin gastrulation?

Back 32

1. The gut divides into 3 parts:

-foregut- esophagus

-midgut- stomach

-hindgut- intestine

2. The mesenchyme differentiates:

-Primary mesenchyme- skeletal rods

-Secondary mesenchyme- coelom, immunocytes, pigment, muscle

--coelom forms via enterocoely

Front 33

Where does involution of amphibian gastrulation start and what type of cells form there?

Back 33

Involution begins at the dorsal marginal zone

Bottle cells mark the site of involution

Front 34

Who is Ray Keller and why is he important?

Back 34

He is a developmental biologist (at the University of Virginia)

Studies neural and mesodermal morphogenesis

He performed explant studies to show autonomous convergent extension morphogenesis in involuting cells

Front 35

Symmetry in the amphibian blastula

Back 35

The blastula appears to have radial symmetry.

It has an A-V axis.

Front 36

Symmetry in the amphibian gastrua

Back 36

The gastrula exhibits bilateral symmetry.

It has 3 axes:

A-V

A-P

D-V

Front 37

Who was Hans Spemann and why is he important?

Back 37

He was a German embryologist

He explored the question: What promotes gastrulation?

He worked with a variety of amphibians and performed a variety of transplant studies to examine the "pre-destiny" of tissues

He won a nobel prize for his work in 1935

Front 38

Describe the Spemann's zygote dissection experiment.

Back 38

The gray crescent in an amphibian embryo can be observed at fertilization.

He cut a zygote through the gray crescent, duplicating the first division, and from the two halves, two complete organisms formed.

He then cut a zygote abnormally, one half had gray crescent and the other did not. The half with gray crescent formed a complete organism. The other half formed a "belly piece"

The sorsal blastopore lip forms at the gray crescent.

Front 39

What did Hans Spemann and Hilde Mangold do together?

Back 39

They performed xenotypic transplants using two different species of newt.

They discovered the organizer (as it relates to the amphibian bauplan)

They described primary induction.

Front 40

Describe Spemann and Mangold's xenotypic newt transplant experiments.

Back 40

They took a portion of the dorsal blastopore lip from the donor newt and transferred it to the ventral region of a host newt.

It caused two invaginations to occr in the blastopore

Conjoined twins, attached ventrally, were produced

Front 41

What is produced from the dorsal blastopore lip?

Back 41

The DBL induces the production of ventral structures.

It produces the notochord (axial mesoderm), the lower part of the neural tube (notoplate) , and part of the somitic mesoderm.

Front 42

Describe primary induction

Back 42

A process specific to vertebrates

Tissue is induced:

chordomesoderm (DBL in amphibians)

the organizer (Spemann-Mangold organizer in ambhibians)

Acts globally to:

specify axes

"establish" germ layers and germ layer regions

induce the CNS

Front 43

Who was Pieter Nieuwkoop and why is he important?

Back 43

He was a Dutch embryologist who specialized in amphibian embryonic anatomy

He researched inductive interactions:

neural induction

mesendoderm induction

germ cell induction

Front 44

Fate of the amphibian blastula regions when isolated

Back 44

Animal cap cells- ectoderm

Vegetalcells- vegetal mass

Ventral marginal zone- mesoderm- blood, epidermis, mesenchyme

Dorsal marginal zone- mesoderm- muscle, neural tube, notochord

Front 45

Recombination of animal cap cells and vegetal cells

Back 45

Mesodermal tissue, such as mesenchyme, muscle, and notochord, is induced.

Vegetal cells are a source of inductive signal

Front 46

Gimlich and Gerhart dorsal vegetal cell transplants

Back 46

UV-Irradiated recipient cells. UV destroys microtubules and the gray crescent can't form because there is no cortical rotation. The UV recipient will form only a belly piece. The UV recipient that got vegetal cells from a donor underwent complete development.

Transplant of vegetal cells to another normal recipient induced a new gastrulation site and additional body axis formation, creating another head located next to the first

Front 47

Where is the Nieuwkoop center and what is its purpose?

Back 47

It is located opposite the site of sperm entry on an embryo.

Autonomous specification causes determinants to move to establish the Nieuwkoop center

The Nieuwkoop center sends signals above itself to the marginal zone, which is induced to become the organizer

Front 48

Which organisms are basal metazoans?

Back 48

porifera and cnidaria

Front 49

Characteristics of porifera

Back 49

sponges

parazoa- not "true" metazoans

asymmetrical body plan

no true germ layers

limited number of cell morphotypes: no muscles or nerves

Resemble a perforated bag

Choanocyte, archeocyte (amebocyte)

Front 50

poriferan development

Back 50

Holoblastic cleavage

Variable cleavage patterns

Form coeloblastulae and/or stereoblastulae

Exhibit widely varied modes of gastrulation and resulting larvae

Front 51

Cnidarian model organisms

Back 51

Hydra

Sea anemone

Front 52

Cnidarian bauplan

Back 52

radial symmetry

diploblasts

-ectoderm- epidermis- sensory cells, cnidoblasts, interstitial cells

-endoderm- gastrodermis- muscle, neurons, gland cells

- mesoglea between the germ layers- ECM, connective tissue

Front 53

Cnidarian embryology

Back 53

Simplistic but varied

Primarily anarchic: no observable patterns

Blastulae: coeloblastulae, stereoblastulae

Gastrulation forms: ingressions, delaminations, invagination, epiboly

Form a planula larva

Front 54

Fate of stem cells in cnidarians

Back 54

Multipotent stem cells create:

-nematocytes

-nerve cells

-gland cells

-egg lineage stem cells -> eggs

-sperm lineage stem cells -> sperm

Front 55

Ecdysozoans model organisms

Back 55

C. elegans

The nematode

Drosophila melanogaster

The fruit fly

Arthropod/insect

Front 56

Ecdysozoa characteristics

Back 56

bilaterans

protostomes

ecdysis- molting

metamerism- body segmentation

Front 57

C. elegans bauplan

Back 57

Pseudocoelomate:

outer tube- hypodermis, muscle

inner tube- digestive tract (including pharynx), reproductive tract, no mesoderm boundary

hermaphrodite gonad

sequential hermaphrodite: male then female:

make sperm, sore it, make eggs, and self-fertalize (internally)

Every adult is identical (959 somatic cells) and has identical development (invariant cell lineage)

Front 58

C. elegans embryology

Back 58

Isolecithal egg, elongate along A-P axis

Holoblastic cleavage; rotational cleavage pattern

24-cell blastula

doesn't undergo true gastrulation- migration of cells is minimal

complete lineage map known

Front 59

C. elegans 4-cell stage

Back 59

AB -> ABp & ABa

P1 -> EMS & P2

Front 60

What is the importance of P granules?

Back 60

They are the determinants of the P cells and their germ line descendants

Front 61

C. elegans founder cells

Back 61

p-cells: germline

C, D: mesoderm

ABa: pharynx, hypodermis, neurons

ABp: hypodermis, neurons

MS: mesoderm, including pharynx

E: endoderm

Front 62

What is the nematode cuticle made of?

Back 62

collagens

Front 63

Drosophila body characteristics

Back 63

head- fused segments used for feeding

thorax- locomotory appendages

abdomes- respiration and reproduction

Front 64

Drosophila reproductive system

Back 64

Ovary composed of ovarioles

Germerium- site of oogonium

Vitellarium- site of egg maturation

Internal fertilization

Spermatheca- sperm storage organs

Front 65

Formation of oocyte and nurse cells

Back 65

4 rounds of mitosis to produce 16 cells

Cells have ring connections.

Only 2 cells have 4 ring connections.

One of these becomes the oocyte. The others become nurse cells.

Front 66

What contributes to Drosophila oocyte maturation?

Back 66

Nurse cells- produce mRNA/ protein determinants

Yolk- fat bodies are the site of yolk production

Follicle cells- induce oocyte (produce vitelline envelope), produce chorion for protection, and produce embryonic polarity

Front 67

Drosophila embryology

Back 67

centrolecithal egg (yolk central)

superficial cleavage (karyokinesis, no cytokinesis)

Front 68

Stages of Drosophila cleavage

Back 68

1. syncytial stage

2. syncytial blastoderm

3. pole cell formation

4. Cellularization

via formation of furrow canals and acquisition of membrane vessicles

Front 69

Drosophila gastrulation events

Back 69

Furrow formation:

ventral furrow (internalization of mesoderm)

cephalic furrow (separate head from body)

Germ band extension

convergent extension of mesoderm and ectoderm

elongation of embryo

formation of gut tube

neuroectoderm ventral ingression

segmentation

Germ band retraction

shorten A-P axis, lengthen D-V axis

Front 70

Long germ band insect development

Back 70

cellular blastoderm produces head, thorax abdomen

Front 71

Short germ band insect development

Back 71

cellular blastoderm produces the head only

the growth zone produces the rest of the organism

Front 72

Intermediate germ band insect development

Back 72

cellular blastoderm produces the head and thorax

the growth zone produces the rest of the organism

Front 73

Lophotrochozoan characteristics

Back 73

bilaterians

protostomes

ciliated

have lophophore, a ciliated feeding structure

Front 74

Eutrochozoan characteristics

Back 74

used ciliated structures for locomotion

trochophore larva

spiral cleavage

Front 75

Examples of Eutrochozoans

Back 75

Annelids - specialization at anterior and posterior ends

anterior = head = acron

posterior = pygidium

Molluscs- veliger- have velum, shell, foot, visceral mass, and shell gland

Nemerteans

Platyhelminthes- flatworms

Front 76

Trochophore larva

Back 76

have apical tuft and apical organ to sense orientation

have trochal band (ciliary ring) for locomotion

Front 77

What is clockwise cleavage called?

Back 77

Dexiotropic

Dextral

Front 78

What is counter-clockwise cleavage called?

Back 78

Laeotropic

Sinistral

Front 79

How are spirally cleaving cells categorized?

Back 79

quadrants: letters: A, B, C, D

quartets: layers

all micromeres derived from one cleavage of the macromeres

numbers

Front 80

Eutrochozoan generalized fate map

Back 80

micromeres: ectoderm of larva

macromeres (after generation of 3rd quartet): larval endoderm

3a, 3b, 3c: (ecto)mesoderm

2d: sometoblast- adult ectoderm

4d: mesentoblast- adult mesoderm and andoderm

Front 81

Annelids growth zone

Back 81

The larval form becomes reorganized to form the head of the adult

The trunk is produced from a growth zone

Front 82

4 stage Eutrochozoan cell isolations

Back 82

A, B, C- produce a subset of cells expected

D- regulates to produce larva- organizer

induced by micromeres- touching the most

always gets polar lobe (extra cytoplasm bubble)

Front 83

Types of chordates

Back 83

Urochordates

Cephalochordates

Vertebrates

Front 84

Types of vertebrates

Back 84

Amniotes- reptiles, birds, mammals- have amnion (fluid-filled tissue that supports development "outside" of water)

Anamniotes- fish, amphibians- lack amnion

Front 85

Vertebrate characteristics

Back 85

Cephalization

Appendages

Endoskeleton of bone and cartilage

Neural crest

Front 86

Hemi- Chordates

Back 86

Half-chordates

Display some chordate features

Front 87

Example of urochordate & characteristics

Back 87

Tunicates

(Ascidians)

((Holoblastic & bilateral cleavage))

((Bilaterally symmetrical coeloblastula))

((Six tissues after gastrulation))

Front 88

What is the myoplasm

Back 88

Tail muscle

Develops from yellow crescent

Front 89

Urochordate gastrulation events

Back 89

Invagination of endoderm

Involution of mesoderm

Epiboly of ectoderm

Front 90

Urocjordate embryology

Back 90

Autonomous specification of most rissues

Conditional signaling from A4.1

Front 91

Cephalochordate example and characteristics

Back 91

Amphioxus

Radial cleavage

256-cell coeloblastula

Similar fate map to urochordates and amphibians

Front 92

Cephalochordate gastrulation events

Back 92

Invagination of endoderm

Front 93

Isolation of cephalochordate cells at 4-cell stage

Back 93

All produce complete larvae

Also, animal tier + vegital tier = complete larvae