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Chapter 1- “The anatomical tradition”
• ______________- progressive change in multicellular organisms
• ___________- study of animal development
• _________________ = development + embryology
Big questions
• What dictates _________________?
• How can cells form ordered ___________?
• How are _________ cells set apart?
• How do cells know when to stop _____________?
• How do cells know where to ___________?
Historical settingPre-1800s - Two theories
1. ___________ theory-– All organs prefigured,
but very small
– Backed by science, religion, philosophy
2. ______________– All organs made de
novo (from scratch)
•Early 1800s- staining techniques/microscopy disprove preformation theory-
•The birth of “_______________”•Late 1800s- _______ (instead of goo) theory
recognized
Fate mapping- the mapping of cell lineage
Strange terminology
• _____________- Organisms with three primary germ layers
• _______________- lack a true mesoderm• Hydra, jellyfish, sponges
• ________________- Cells receiving cues from other cells
Four Principles-“Von Baer’s laws”
1. ___________features appear prior to ______________ ones– All vertebrates have gill arches, notochords, primitive kidneys
2. Less general characters are developed from _______ general (i.e. specialized from non-specialized)– Scales vs. feathers– Legs vs. wings– Nails vs. claws
3. An embryo does not pass through the ___________________ of other, lower creatures
4. Thus, the early embryo of a higher animal in never like a lower animal, but only like it’s ___________________.– Humans never look like ____________
Fate mapping
Major layers-1. _____________-
• Outer embryo layer• Skin• Nerves
2. ______________-• Inner embryo layer• Digestive tract• Respiratory system
3. _____________-• Middle layer• Blood• Heart• Kidney• Gonads• Bones• Connective tissue• Muscle
Commit these to memory
“Homologous” vs “Analogous”
• “________________”- Similarity arising from a common ancestral structure– e.g. bird wing and
human arm• “_______________”-
Similar function, but not common ancestor– e.g. bird wing and
insect wing
Human arm
Seal limb
Bird wing
Bat wing
Teratology
• Environmental agents causing disruption of development -called “________________”
• Example- __________________ (1961)
Chapter 2- Life cycles
• All animals follow similar life cycle– __________________- mixing of genetic
material between sperm and egg – ___________________- events between
fertilization and hatching (or birth)
1. __________- One cell is subdivided into many cells to form a blastula
2. _________________- Extensive cell rearrangement to form endo-, ecto- and meso-derm
3. ____________________- Cells rearranged to produce organs and tissue
4. _________________- produce germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells
General Animal Development
01ear.mov
The Frog Life cycle
Unfertilized egg(Stained)
100’s of fertilized eggs
Vegetal pole
Animal pole
Single egg, early blastula
Note: Cells get smaller, but egg ___________ remains the same!
The Frog Life cycle- gastrulation through neurula
1. _______________________________ forms at “belly”
2. Dorsal blastopore lip becomes the ____________ (a circle)
3. Ectoderm cells encase 4. Mesoderm cells migrate inside
along blastopore edges
5. Neural folds and groove appear
Fig. 2.3
The Frog Life cycle- metamorphosis
A unicellular protistThe “goo” theory can work!
A single cell3 cm long!
What happens if we swap nuclei??Species 1 Species 2
Nucleus(in Rhizoid)
Sexual reproduction
•Bacteria, amoeba- Reproduction without sex
•_________________- Sex without reproduction
Sex and reproduction are two distinct processes•Sex- mixing of genetic material from two individuals•Reproduction- creation of new individuals
Swap “micronuclei” then separate
•________________- Sex with reproduction
Sexualreproduction
Asexualreproduction
Chlamydomonas(A eukaryote)
Fig. 2.8
Chromosome mixing
“Plus” “Minus”
“Plus” “Minus”
Unicellular eukaryotes have basic developmental processes observed in higher organisms-
•Mitosis and meiosis is accomplished•Sexual reproduction•Chromosomal structure is stable and similar
But, multicellular organisms are a whole new ball game
These require cell-cell communication and distinct cell functions“_________________________________”
Example – Volvox
Chlamydomonas Gonium Panadorina
Eudorina Pleodorina Volvox
Single cell
Principle 1 :One cell ______________ into 4-64 cells
Principle 2 :___________________ of cell types-
somatic vs reproductive
2000 cells
Germ cells
Somatic cells(appear as dots)
Fig. 2.11
Example – Volvox
Principle 3 : _______ cells instructed to perform specific functionsMulticellular aggregation to from a slug- Dictystelium
>10,000 cell _____________
A _______ is formed
(2-4 mm )
Travel to new food source
Differentiate into _______ and spore case
Stalk dies, spores released
Individual cells Start here
Fig 2.17
This cyclerequires adhesion, _____________
and ______________.
1. ________- One cell is subdivided into many cells to form a blastula
2. __________- Extensive cell rearrangement to form endo-, ecto- and meso-derm
3. _____________- Cells rearranged to produce organs and tissue
4. _______________- produce germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells
General Animal Development (From chapter 2)
Chapter 3- Experimental Embryology• Three major approaches
1. External forces - ____________________
2. Internal forces- ____________________
3. Organ development (Morphogenesis)
1. External forces
a. Sex determination•Boellia- depends on where larva lands•Alligator egg temperature - <30C = _________ development
b. Embryo ______________•Butterflies- colors depend in season•Frogs and UV light
Fig. 3.1
Summer
Spring
Chapter 3- Experimental Embryology2. Internal forcesA few definitions____________________- development of specialized cell types ____________________- developmental fate is restricted
Two stages- 1. ___________________- capable of becoming specific
cell types, but decision is reversible2. __________________- non-reversible cell fate decision
a. __________________specification- blastomere cell fate is determined at blastula stage (e.g. isolated blastomere will become same type if
removed from blastula)
Most ________________ do this
Chapter 3- Experimental Embryology2. Internal forces (continued)
b. ______________ specification- cell fate is determined on where a cell finds itself (e.g. isolated blastomere will become what surrounding cells dictate)
All ___________ do this
Fig. 3.11
Transplant cells
Normal development
Removed cells are compensated
Cell fate dictated by location
c. Note- insects display __________ Specification-cell fate is determined in egg cytoplasm
Chapter 3- Experimental Embryology
More definitions- __________- soluble molecule that instructs cells to differentiateConcentration ___________- A morphogen at different concentrations
depending on location of cell
Example of concentration gradient- the flatworm (Hydra)
It grows back! The French flag analogy to understand
gradients
2. Internal forces (continued)
A lot makes blue
A little makes red
A modest amount makes white
Fig. 3.19
French Flag Analogy
Transplanted tissue retainit’s _____________, but
differentiates according to
new _______________
2. Internal forces (continued)
An example of a concentration gradient- Activin levels dictate cell fate in Xenopus
Activin levels
Fig. 3.20
2. Internal forces (continued)
A _________________ field- a group of cells whose position and fate are specified with respect to the same set of boundaries.
•The general fate of a cell group (e.g. tissue) is determined, but individual cells within that tissue can respond to new positional cues
Example- a “_______ field”-Transplantation of cells specified for limb development results in limb formation in new place-But nearby cells will form a limb
Salamander If remove limb bud, surrounding cells will form the limb
Nematode infection disrupts normal limb field
Tree frog
Fig. 3.22
2. Internal forces (continued)
3. Morphogensis
Morphogenesis is the bigger question of how cells within a given organ are in a precise place and have a precise function.
1. How are _________formed from populations of cells?2. How are __________ constructed from tissues?3. How do organs form in particular ____________, and
how do migrating cells reach their destinations?4. How do organs and their cells grow, and how is growth
____________________ throughout development?5. How do organs achieve ____________? Compare leg and
finger cross-sections- the same yet different.
3. Morphogensis (continued)
Observations- Mix cells from different cell types in a culture dish, they migrate to pre-instructed location.
Mesoderm+ epidermis
Mesoderm+ endoderm
Mesoderm+ endoderm+epidermis
How do the cells “know” where to go?
One model- The ____________ modelMalcolm Steinberg 1964
3. Morphogensis (continued)
Cells interact so as to form an aggregate with the smallest_________________free energy
The _____________ model 20.1
Surface tension
8.5
12.6
4.6
1.6 Fig. 3.30
Adhesion is dictated by 1. Number of cell adhesion molecules2. Type of cell adhesion molecules
In other words, those with stronger _________ properties move to the _________ of a cell mass
3. Morphogensis (continued)
_____________ – Calcium-dependent adhesion proteins- a major class of proteins that mediate cell adhesion
•Establish intercellular connections•Required for _____________ segregation•Required for organization of animal formation
Cadherins bind to __________in cells, which bind to actin cytoskeleton
Fig. 3.31
Catenins
Cadherin
3. Morphogensis (continued)
___-cadherin- in all mammalian embryos, then restricted in epithial tissues of embryos and adults
Cadherins are responsible for cell sorting
Cadherin types
Fig. 3.31
Cells with different ___________ sort
Cells with different cadherin _____sort
___-cadherin- primarily in placenta___-cadherin- in mesoderm and developing central nervous system
____-cadherin-required for blastomere adhesion