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
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1.
2.
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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