1. Genes and Development
CVHS
Chapter 16

2. Development All the changes that occur during an organism’s lifetime
Cell specialization:
Cell determination: specific patterns of gene activity
Cell differentiation: final step of cell specialization
16_03CellSignaling_A.swf

3. Morphogenesis The development of the body plan Requires two steps:
Cell differentiation
Maternal Influences: cytoplasmic determinants
Spatial organization
These depend on:
Pattern formation, cell signaling, cell shapes, cell migrations
Regulatory genes that turn other genes on and off at appropriate times
Homeotic Genes (Hox Genes)

4. (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)
18_19HeadTailAxisFruitFly_A.swf 4

5. Zygote
The fertilized egg that develops into all the specialized cells needed within a multicellular organism
Each specialized type of cell makes a unique set of proteins
This is true despite the fact that these cells show nuclear equivalence – in other words they have the same genes

6. 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) 6

7. Cloning A new individual that is genetically identical
In plants: have been able to make a clone from somatic (body) cells of an adult plant
In animals: have produced clones by transferring the nucleus of a cell into an enucleated egg cell
1996: Dolly – cloned sheep in Scotland
Other mammals have been cloned since
Problems: only 1% - 2% success rate; high incidence of genetic defects

8. Dolly the Sheep

9. Rainbow and CC
Cloned at Texas A & M in 2001, CC (copy cat) is not the same color as her clone, Rainbow & they have different temperments.

10. Human cloning
Reproductive cloning – goal is making a new individual… very controversial and ‘banned’
Therapeutic cloning – goal is NOT making a new person but producing stem cells

11. Stem Cells
Undifferentiated cells that can divide to produce differentiated cells and retain the ability to reproduce themselves
Totipotent: potential to give rise to all body tissues
Pluripotent: more specialized; can give rise to many but not all types of cells

12. Stem cells… Potential uses: Potential sources:
Cures for degenerative diseases such as Parkinson’s
Potential sources:
Unused human embryos from fertility clinics and newborn’s umbilical cord blood

13. Parkinson’s Disease
Degenerative Brain cell disorder that causes movement difficulties. Linked possibly to a specific protein within brain cells.

14. Control of cellular DNA expression
Differential gene expression (Ch. 13)
Genomic rearrangements: physical changes in the structure of the gene eg: immune system cells do this in order to produce new antibodies in response to infection
Gene amplification: the copies of a particular gene are increased so that the amount of transcription of that gene can be increased

15. Genetic control of development:
Very similar controls exist in a wide variety of organisms:
The basic mechanism evolved early and has been maintained although modified
Maternal effect genes:
Organize the structure of the egg cell
Help establish the polarity of the embryo: dorsal/ventral and anterior/posterior
Homeotic genes:
Specify the developmental plan for each body part

16. Genetic control of development…
Induction: cell differentiation is influenced by interactions with neighboring cells
Chronogenes: involved in developmental timing
Apoptosis – programmed cell death
Eg: skin between human fingers

17. Cancer and Cell Development
All forms of cancer have one thing in common: no divisional regulation of cells
Tumor: a localized group of cells with uncontrolled cell division
Metastasis – cancer cells ‘escape’ and spread to other parts of the body
Tumors that can metastasize are malignant

18. Cancer and Cell Development…
Genes that control cell division:
Proto-oncogenes – normal genes that control cell division
Mutations can change these into oncogenes – cancer genes
Some viruses carry oncogenes
Tumor suppressor genes – also put the ‘brakes’ on cell division
Mutations can turn off these genes and therefore stop the suppression of a tumor

19. P 53 & RAS Gene Mutations
Mutations in the ras proto-oncogene and p53 tumor-suppressor gene are common in human cancers
Mutations in the ras gene can lead to production of a hyperactive Ras protein and increased cell division

20. Ras protein active with or without growth factor.
Figure 16.17 1
Growth factor 3
G protein
Ras 6 5
Protein that
stimulates
the cell cycle
NUCLEUS
GTP
Transcription
factor (activator) 2
Receptor 4
Protein
kinases
MUTATION
Ras
NUCLEUS
Figure Normal and mutant cell cycle–stimulating pathway
Overexpression
of protein
Transcription
factor (activator)
GTP
Ras protein active with
or without growth factor. 20

21. Protein kinases Protein that inhibits the cell cycle NUCLEUS UV light
Figure 16.18 2
Protein kinases
Protein that
inhibits the
cell cycle
NUCLEUS UV
light 1
DNA damage
in genome 3
Active form
of p53
Inhibitory
protein
absent
Figure Normal and mutant cell cycle–inhibiting pathway
Defective
or missing
transcription
factor UV
light
MUTATION
DNA damage
in genome 21