Developmental Biology

How does
a fertilized
egg become
an
animal?

Clam egg and sperm

Developmental Biology is the study of a PROCESS whereby a single

To form an embryo, the following (and more!) must occur:
Gametes

Differentiation is a central idea of development:
All cells have the same

Nature supports an incredible diversity of plant and animal body plans

Yet all of these organisms share conserved developmental mechanisms that are

Developmental Biology is studied using the following TOOLS
Cell Biology
Genetics
Molecular Biology

Let’s Review the Basics

The body is made of millions to billions

Development Occurs at an Unfamiliar Scale

If a cell was the size

Development Occurs at an Unfamiliar Scale

If a protein was the size

Two Extreme Models for Differentiation
from the late 1800’s (neither is correct)
Mosaic

Roux’s landmark experiments with frog embryos:
do cells have

Roux’s landmark experiments

Figure 3.16. Destroying (but not removing) one cell of

Driesch’s experiments with sea urchin embryos:
do cells have

C. elegans

How do cells know which genes to
activate as they go

Information from parents:
The Cell lineage

But what makes “red” different from “blue”

Mother cell

Unequal localization

of "determinants"

Cell division transfers

determinants to a single

Mother cell

Cell interactions

Cell type A

an alternative mechanism to generate

Cells don’t have to be inside an animal to
communicate with

These cell-cell signals
lead the yeast cells
that receive them to
move together,

The slime mold develops into an animal only when it (they?)

The remarkable life cycle of a slime mold

cAMP signal

Slug/Grex

Figure 2.10

Dictyostelium discoideum (slime mold) slug stage

The Cells of the Grex Differentiate

Conclusion:
Even cells of the most simple eukaryotic organisms sense their

Breakthroughs in Modern Biology

1. All organisms share similar cellular machinery
2. All