Genes and Development

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Genes and Development

• Chapter 16

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Development

• All the changes that occur during an organisms
  lifetime
• Cell specialization
• Cell determination specific patterns of
  gene activity
• Cell differentiation final step of cell
  specialization

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Morphogenesis

• 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

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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

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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

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Dolly the Sheep
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Rainbow and CC
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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

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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

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Stem cells

• Potential uses
• Cures for degenerative diseases such as
  Parkinsons
• Potential sources
• Unused human embryos from fertility clinics and
  newborns umbilical cord blood

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Control of cellular DNA expression

1. Differential gene expression (Ch. 13)
2. 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

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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

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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

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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

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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