Warm up Questions

1. A retinal cell (a cell found in the retina of your eye) has the same genetic information as a skin cell. What makes these two cells so different?

2. How do you think the fate of a cell is determined early on in embryonic development?

Ideas

Questions about Cell Differentiation and Embryonic Development

Cellular Differentiation in Embryonic Development

Early Embryonic Development

• Gastrulation happens differently in different organisms, but all vertebrates will have the three germ layers

Cellular Differentiation

There are two mechanisms of cell differentiation in embryonic development:

1. Cytoplasmic Segregation

2. Embryonic Induction

Cytoplasmic Segregation• Cells in different germ layers look very similar, so

what is different about them?

• An egg has substances called maternal determinants• Maternal determinants are not distributed equally in the

cytoplasm

• Their concentration determines the fate of a cell

Embryonic Induction

• Cell specialization is also influenced by signals given off by neighboring cells

• Induction is the ability of one embryonic tissue to influence the development of another• Happens through large proteins called inducers

Embryonic Induction

Blue = ectodermPink = mesodermOrange = endoderm

How could we design an experiment to tell whether one of these tissue types can induce development of a body region?

Spemann/Mangold Experiment ReenactmentReenactment video

Summary

• In embryonic development, chemical signals within a cell and across cells can determine the pathway a cell takes (ex. nerve cell, heart cell, etc.)

• The distribution of maternal determinants in the cytoplasm of the egg lead to a body plan for the zygote

• Some tissue types can induce development of that tissue in surrounding cells using signal proteins called inducers

Stem Cell Video Focus Questions

1. How does an embryonic cell “know” what specific type of cell to become?

2. What is an embryonic stem cell, and what is an adult stem cell?

3. What are some ways that stem cells are being used in research?

HHMI Stem Cells video