Figure 20.1 Sperm and Egg Differ Greatly in Size

Figure 20.4 Patterns of Cleavage in Four Model Organisms (Part 1)

Figure 20.4 Patterns of Cleavage in Four Model Organisms (Part 2)

Figure 20.5 The Mammalian Zygote Becomes a Blastocyst (Part 2)

Figure 20.7 Twinning in Humans

Two BlastulasTwo Blastulas

zygote

blastula

gastrulaendoderm

glands

pancreas, liver

lining ofrespiratory tract

lining ofdigestive tract

pharynx

mesoderm circulatorysystem

blood, vessels

somites

ectoderm

gonads

kidney

ventralnerve cord

neural crest

chordates vertebrates

integuments

lining ofthoracic and

abdominal cavities

outer covering of internal organs

dermissegmented

muscles

brain,spinal cord,

spinal nerves

gill arches,sensory ganglia,

Schwann cells,adrenal medulla

notochord

heart

skeleton

The Primary The Primary Germ LayersGerm Layers

epidermis

Figure 20.8 Gastrulation in Sea Urchins

Figure 20.9 Gastrulation in the Frog Embryo (Part 1)

Figure 20.9 Gastrulation in the Frog Embryo (Part 2)

Figure 20.9 Gastrulation in the Frog Embryo (Part 3)

NeurulationNeurulation“For the real amazement, if you wish to be amazed, is this process. You start out as a single cell derived from the coupling of a sperm and an egg; this divides in two, then four, then eight, and so on, and at a certain stage there emerges a single cell which has as all its progeny the human brain. The mere existence of such a cell should be one of the great astonishments of the earth. People ought to be walking around all day, all through their waking hours calling to each other in endless wonderment, talking of nothing except that cell.”

--Lewis Thomas

Figure 20.15 Neurulation in the Frog Embryo (Part 1)

Figure 20.15 Neurulation in the Frog Embryo (Part 2)

Figure 20.16 The Development of Body Segmentation

Figure 20.10 Spemann’s Experiment

Figure 20.11 The Dorsal Lip Induces Embryonic Organization

Figure 20.2 The Gray Crescent

Figure 20.3 Cytoplasmic Factors Set Up Signaling Cascades

Figure 20.12 Molecular Mechanisms of the Primary Embryonic Organizer

NC

Shh

sclerotome

dermomyotomemotorneurons

fp

dorsal epidermal ectoderm

NTWnt?

somite

Wnt

BMP-4FGF5?

lateral mesoderm

NT-3

multiple signals pattern the vertebrate neural tube and somite

Figure 19.9 Embryonic Inducers in the Vertebrate Eye

Induction in eye development

Figure 19.10 Induction during Vulval Development in C. elegans (Part 1)

Figure 19.10 Induction during Vulval Development in C. elegans (Part 2)

Origami:sets of instructions

(programs)to build 3-D models of organisms out of

paper –Is this how

developmental programs work?

DifferentiatedCell Types

B C D E F G HA

Differentiation

Determination

The “landscape” of developmental programs:The determination of different cell types involvesprogressive restrictions in their developmental potentials. When a cell “chooses” a particular fate, it is said to be determined. Differentiation follows determination, as the cell elaborates a cell-specific developmental program.

40Mouse Liver ProteinsMouse Liver Proteins Mouse Lung ProteinsMouse Lung Proteins

2-D Electrophoresis of proteins extracted from two 2-D Electrophoresis of proteins extracted from two different mouse tissuesdifferent mouse tissues

AA BB

Cell types A & B share a common set of “housekeeping” gene products and a set of

unique “luxury” gene products that represent the A or B developmental program

Cell types A & B share a common set of “housekeeping” gene products and a set of

unique “luxury” gene products that represent the A or B developmental program

A & BA & B

Sets of gene productsin two cell types

Figure 19.2 Developmental Potential in Early Frog Embryos

Figure 19.3 Cloning a Plant (Part 1)

Figure 19.3 Cloning a Plant (Part 2)

Figure 19.4 A Clone and Her Offspring (Part 1)

Figure 19.4 A Clone and Her Offspring (Part 2)

Figure 19.4 A Clone and Her Offspring (Part 3)

Figure 19.5 Cloned Mice

21_41_cloning.jpg

What is a stem cell?

differentiated cell

determined cell

stem cell

21_39_hemopoietic.jpg

Recent breakthroughs in stem cell research :

- stem cells can be obtained from adults and embryos/fetal tissue

- stem cells are multipotent!

-this very likely has theraputic value

DifferentiatedCell Types

B C D E F G HA

Differentiation

Determination

The “landscape” of developmental programs:The determination of different cell types involvesprogressive restrictions in cellular developmental potentials. When a cell “chooses” a particular fate, it is said to be determined. Differentiation follows determination, as the cell elaborates a cell-specific developmental program.

Uses of human embryos

• obtain stem cells

• somatic cell transfer, then obtain stem cells

• use stem cells that are coaxed to develop into different tissues for therapeutic purposes

Figure 20.14 A Human Blastocyst at Implantation

Week 1

Week 2

Week 4

Week 3

Week 5

Figure 19.6 The Potential Use of Embryonic Stem Cells in Medicine (Part 1)

Figure 19.6 The Potential Use of Embryonic Stem Cells in Medicine (Part 2)

Figure 19.7 Asymmetry in the Early Embryo (Part 1)

Figure 19.7 Asymmetry in the Early Embryo (Part 2)

Figure 19.8 The Principle of Cytoplasmic Segregation

Figure 19.9 Embryonic Inducers in the Vertebrate Eye

Figure 19.11 Apoptosis Removes the Tissue between Fingers

Figure 19.12 Organ Identity Genes in Arabidopsis Flowers (Part 1)

Figure 19.12 Organ Identity Genes in Arabidopsis Flowers (Part 2)

Figure 19.13 A Nonflowering Mutant

c.

b.

Nursecells

AnteriorPosterior

Movement ofmaternal mRNA

Oocyte

Folliclecells

Fertilized egg

a.

d.

e.

Three larval stages

Syncytial blastoderm

Cellular blastoderm

Nuclei line up alongsurface, and membranesgrow between them toform a cellular blastoderm.

Segmented embryo prior to hatching

Metamorphosis

Abdomen

Thorax

Head

Hatching larva

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Nucleus

Embryo

Egg with maternally-depositedmRNA

A P

bicoid nanos

Gradients of informational proteinsencoded by maternal mRNA

Gap Genes

KnirpsKrupplehunchback

Pair RuleGenes

Segment PolarityGenes Homeotic

Genes

Figure 19.15 A Gene Cascade Controls Pattern Formation in the Drosophila Embryo

Fig. 19.13

Figure 19.14 Bicoid and Nanos Protein Gradients Provide Positional Information (Part 1)

Figure 19.14 Bicoid and Nanos Protein Gradients Provide Positional Information (Part 2)

hunchback & Krupple - gap class

even skipped - pair rule class

fushi tarazu (ftz) & even skipped (eve) - pair rule class

engrailed - segment polarity class

Fig. 19.17

40wild-type Antennapedia

mutant

Fly heads

Fig. 19.18

40Hoxb-4 knockoutwildtype

mouse

40