Tortipotent
An entire plant can be generated from one cell. Most cells are tortipotent.
Transgenic Animal
One whose genetic composition has been altered by the addition of exogenous DNA
Transgene
DNA introduced into a transgenic animal
Germ Lines
Cells that produce gametes (sperm or egg). Changes in cells can be passed to offspring.
Somatic Cells
Cells that make up the majority of the body (non-germ line cells)
Name 3 ways DNA is introduced into mice
- Retroviral Vectors
- Microinjection
- Embryonic Stem Cells
Retrovirus
Eukaryotic RNA virus that can form double-stranded DNA copies of their own genome. The ds copies integrate into an infected host cell’s genome.
Retroviral Vector Method
- Embryos infected with transgene containing retrovirus
- Embryo implanted in female
- Pups are screened for insertion
- New lines established from pups with transgene in germ line cells
Drawbacks to Retroviral Vector Method
- Applications limited in size (8 kb of DNA)
- Organisms could become carrier of virus if viral genetic content also incorporated
- Rarely used for commercial products
DNA Microinjection Method
Preferred Method
- Females are induced to super ovulate (35 eggs rather than 5-10)
- Females are killed and eggs are harvested
- Microinjection occurs immediately in male pronuclei (because it’s larger)
- Implanted in female, pups delivered in 3 weeks
- PCR from tail identifies transgenic offspring
- Mating tests determine if transgene present in germ line
Drawbacks to DNA Microinjection Method
Inefficient - at best 5% of eggs become live transgenic animals
