1. Development, Stem Cells, and Cancer16
Development, Stem Cells, and Cancer

2. Concept 16.1: A program of differential gene expression leads to the different cell types in a multicellular organism
transformation from zygote to adult results from cell division, cell differentiation, and morphogenesis
Cell differentiation - process by which cells become specialized in structure and function
Morphogenesis - the processes that give an organism its shape 2

3. (a) Fertilized eggs of a frog (b) Newly hatched tadpole
Figure 16.2
Figure 16.2 From fertilized egg to animal: What a difference four days makes.
1 mm
2 mm
(a) Fertilized eggs of a frog
(b) Newly hatched tadpole 3

4. (a) Cytoplasmic determinants in the egg (b) Induction by nearby cells
Figure 16.3
(a) Cytoplasmic determinants in the egg
(b) Induction by nearby cells
Unfertilized egg
Early embryo
(32 cells)
Sperm
Nucleus
Fertilization
Molecules of
two different
cytoplasmic
determinants
Zygote
(fertilized
egg)
NUCLEUS
Signal
transduction
pathway
Mitotic
cell division
Figure 16.3 Sources of developmental information for the early embryo
Signal
receptor
Two-celled
embryo
Signaling
molecule
(inducer) 4

5. Induction - signal molecules from embryonic cells cause transcriptional changes in nearby target cells 5

6. Sequential Regulation of Gene Expression During Cellular Differentiation
Determination commits a cell irreversibly to its final fate
Determination precedes differentiation 6

7. Master regulatory gene myoD
Figure
Nucleus
Master regulatory
gene myoD
Other muscle-specific genes
DNA
Embryonic
precursor cell
OFF
OFF
Figure Determination and differentiation of muscle cells (step 1) 7

8. Master regulatory gene myoD
Figure
Nucleus
Master regulatory
gene myoD
Other muscle-specific genes
DNA
Embryonic
precursor cell
OFF
OFF
mRNA
OFF
MyoD protein
(transcription
factor)
Myoblast
(determined)
Figure Determination and differentiation of muscle cells (step 2) 8

9. Master regulatory gene myoD
Figure
Nucleus
Master regulatory
gene myoD
Other muscle-specific genes
DNA
Embryonic
precursor cell
OFF
OFF
mRNA
OFF
MyoD protein
(transcription
factor)
Myoblast
(determined)
Figure Determination and differentiation of muscle cells (step 3)
mRNA
mRNA
mRNA
mRNA
Myosin, other
muscle proteins,
and cell cycle–
blocking proteins
MyoD
Another
transcription
factor
Part of a muscle fiber
(fully differentiated cell) 9

10. Apoptosis: A Type of Programmed Cell Death
Apoptosis is the best-understood type of “programmed cell death” 10

11. Cells undergoing apoptosis
Figure 16.6
1 mm
Interdigital tissue
Cells undergoing apoptosis
Space between digits
Figure 16.6 Effect of apoptosis during paw development in the mouse 11

12. Genetic Analysis of Early Development: Scientific Inquiry
Edward B. Lewis, discovered the homeotic genes, which control pattern formation in late embryo, larva, and adult stages 12

13. Wild type Mutant Eye Leg Antenna Figure 16.8
Figure 16.8 Abnormal pattern formation in Drosophila
Leg
Antenna 13

14. Totipotent cells
Cells that can give rise to all specialized cell types are called totipotent 14

15. Egg with donor nucleus activated to begin development
Figure 16.11
Experiment
Frog embryo
Frog egg cell
Frog tadpole UV
Fully differ-
entiated
(intestinal) cell
Less differ-
entiated cell
Donor
nucleus
trans-
planted
Donor
nucleus
trans-
planted
Enucleated
egg cell
Egg with donor nucleus
activated to begin
development
Results
Figure Inquiry: Can the nucleus from a differentiated animal cell direct development of an organism?
Most develop
into tadpoles.
Most stop developing
before tadpole stage. 15

16. genetically identical to mammary cell donor Results
Figure 16.12
Technique
Mammary
cell donor
Egg cell
donor 1 2
Nucleus
removed
Cultured
mammary
cells
Egg cell
from ovary 3
Cells fused
Cell cycle
arrested,
causing cells to
dedifferentiate
Nucleus from
mammary cell 4
Grown in culture
Early embryo
Figure Research method: reproductive cloning of a mammal by nuclear transplantation 5
Implanted in uterus
of a third sheep
Surrogate
mother 6
Embryonic
development
Lamb (“Dolly”)
genetically identical to
mammary cell donor
Results 16

17. Figure 16.13
Figure CC, the first cloned cat (right), and her single parent 17

18. Stem Cells of Animals
A stem cell - unspecialized cell that can differentiate into specialized cells of one or more types 18

19. Cell division White blood cells
Figure 16.14
Stem cell
Cell
division
Stem cell
and
Precursor cell
Figure How stem cells maintain their own population and generate differentiated cells
Fat cells or
Bone cells or
White
blood cells 19

20. Embryonic stem cells Adult stem cells
Figure 16.15
Embryonic
stem cells
Adult
stem cells
Cells that can generate
all embryonic cell types
Cells that generate a limited
number of cell types
Cultured
stem cells
Different
culture
conditions
Figure Working with stem cells
Different
types of
differentiated
cells
Liver cells
Nerve cells
Blood cells 20

21. Embryonic Stem (ES) cells are pluripotent, capable of differentiating into many cell types
Researchers using retroviruses can reprogram fully differentiated cells to act like ES cells
Cells transformed this way are called iPS, or induced pluripotent stem cells 21

22. Concept 16.3: Abnormal regulation of genes that affect the cell cycle can lead to cancer
The gene regulation systems that go wrong during cancer are the same systems involved in embryonic development 22

23. Types of Genes Associated with Cancer
oncogenes - cancer-causing genes
The normal version of these genes, called proto-oncogenes, code for proteins that stimulate normal cell growth and division 23

24. within the gene within a control element
Figure 16.16
Proto-oncogene
Proto-oncogene
Proto-oncogene
Translocation
or transposition:
gene moved to
new locus, under
new controls
Gene amplification:
multiple copies of
the gene
Point mutation:
within
the gene
within a control
element
Oncogene
Oncogene
Oncogene
New
promoter
Figure Genetic changes that can turn proto-oncogenes into oncogenes
Normal growth-
stimulating protein
in excess
Normal growth-
stimulating protein
in excess
Normal growth-
stimulating
protein in
excess
Hyperactive or
degradation-
resistant
protein 24

25. Tumor-suppressor genes encode proteins that help prevent uncontrolled cell growth25

26. Inherited Predisposition and Other Factors Contributing to Cancer
Individuals can inherit oncogenes or mutant alleles of tumor-suppressor genes 26

27. DNA breakage can contribute to cancer, thus the risk of cancer can be lowered by minimizing exposure to agents that damage DNA, such as ultraviolet radiation and chemicals found in cigarette smoke
Also, viruses play a role in about 15% of human cancers by donating an oncogene to a cell, disrupting a tumor-suppressor gene, or converting a proto-oncogene into an oncogene 27