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