These animals should eventually prove to be valuable sources of
proteins for human therapy.
Transgenic mice have provided the tools for exploring many
A normal mouse cannot be infected with polio virus. The mice
lack the cell-surface molecule that, in humans, serves as the
receptor for the virus. Normal mice cannot serve as an
inexpensive and easily-manipulated model for studying the
disease. With transgenic mice showing the human gene for the
polio virus receptor they can be infected by polio virus and
even develop paralysis and other pathological changes
characteristic of the disease in humans.
There are two methods of producing transgenic mice that are
widely used. Transforming embryonic stem cells (ES cells)
growing in tissue culture with the desired DNA and injecting the
desired gene into the pronucleus of a fertilized mouse egg.
The Embryonic Stem Cell Method "1"
Embryonic stem cells are gathered from the inner cell mass of
mouse blastocysts. They can be grown in culture and retain their
full potential to produce all the cells of the mature animal,
including its gametes.
1. Make your DNA
Using recombinant DNA methods you build molecules of DNA
containing the gene you desire (e.g., the insulin gene) vector
DNA to enable the molecules to be inserted into host DNA
molecules, then promoter and enhancer sequences to enable the
gene to be expressed by host cells.
2. Transform ES cells in culture
This is achieved by exposing the cultured cells to the DNA so
that some will incorporate it.
3. Select for successfully transformed cells.
4. Inject these cells into the inner cell mass of mouse
5. Embryo transfer
Prepare a pseudopregnant mouse by mating a female mouse with a
vasectomized male. The stimulus of mating provokes the hormonal
changes needed to make her uterus receptive.
Then transfer the embryos into her uterus hoping that they
implant successfully and develop into healthy pups.
6. Test her offspring
This is done by removing a small piece of tissue from the tail
to examine its DNA for the desired gene. No more than 10–20%
will have it, and they will be heterozygous for the gene.
7. Establish a transgenic strain
Mate two heterozygous mice and screen their offspring for the 1
in 4 that will be homozygous for the transgene.
Mating these will found the transgenic strain.
The Pronucleus Method "2"
1. Prepare your DNA as in Method 1
2. Transform fertilized eggs
Harvest freshly fertilized eggs before the sperm head has become
a pronucleus and Inject the male pronucleus with your DNA. When
the pronuclei have fused to form the diploid zygote nucleus,
allow the zygote to divide by mitosis to form a 2-cell embryo.
3. Implant the embryos in a pseudopregnant foster mother and
proceed as in Method 1.
A mouse can be annoying where mice can be a bigger problem!
Getting rid of mice can be done in many ways such as the use of
traps that kill or catch and poisons. Controlling mice in and
around your home must be taken seriously as they can introduce
illnesses to your family as well as transfer fleas to pets.