Chapter 16: Genes and Development
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Transcript Chapter 16: Genes and Development
Genes and Development
Chapter 16
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
Morphogenesis
1.
2.
The development of the body plan
Requires two steps:
Cell differentiation
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
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
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
Dolly the Sheep
Rainbow and CC
Human cloning
1. Reproductive cloning – goal is
making a new individual… very
controversial and ‘banned’
2. Therapeutic cloning – goal is NOT
making a new person but producing
stem cells
Stem Cells
Undifferentiated cells that can divide to
produce differentiated cells and retain
the ability to reproduce themselves
1. Totipotent: potential to give rise to all
body tissues
2. Pluripotent: more specialized; can
give rise to many but not all types of
cells
Stem cells…
Potential uses:
Cures for degenerative diseases such as
Parkinson’s
Potential sources:
Unused human embryos from fertility
clinics and newborn’s umbilical cord blood
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
3. Gene amplification: the copies of a
particular gene are increased so that the
amount of transcription of that gene can be
increased
1.
2.
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
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
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
– cancer cells ‘escape’ and
spread to other parts of the body
Tumors that can metastasize are
malignant
Metastasis
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
suppressor genes – also put the
‘brakes’ on cell division
Tumor
• Mutations can turn off these genes and
therefore stop the suppression of a tumor