492865
Description
Mind Map by Lydia Buckmaster, updated more than 1 year ago
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Created by Lydia Buckmaster
over 10 years ago
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Transgenics
- Cross species
transfer of
genetic material
- A transgenic animal is
genetically modified to
contain a gene from
another species
(including gene addition,
removal or modification)
- Aim is to produce
a stable and
heritable change in
the genetic makeup
of an animal
- Knock ins
- Placing genes
at specific loci
- Placing genes
at specific loci
- Knock outs
- Removing
genes
- Removing
genes
- Used to control gene
function, increase
disease resistance,
modify metabolism or
production traits and
to produce
pharmaceuticals
- Xenotransplantation
- Transplantation of
living cells, tissues
or organs from one
species to another
- Transplantation of
living cells, tissues
or organs from one
species to another
- A transgenic animal is
genetically modified to
contain a gene from
another species
(including gene addition,
removal or modification)
- Methods of
Producing
Transgenic
Animals
- Pronuclear
Injection
- DNA extracted
for the gene of
interest
- Several hundred copies
are injected directly into
one (or both) pronuclei
of the fertilised zygote
- Integration of many
copies tends to happen at
a single random point
during the many rounds of
replication of the cells
- After injection,
the embryos are
returned directly
to a surrogate
- After injection,
the embryos are
returned directly
to a surrogate
- Integration of many
copies tends to happen at
a single random point
during the many rounds of
replication of the cells
- Several hundred copies
are injected directly into
one (or both) pronuclei
of the fertilised zygote
- 10-20%
success
rate in mice
- 1-10%
success rate in
farm animals
- Most animals
produced are
not transgenic
- There is great
variation in transgene
expression between
transgenic individuals
- Genes can be added, but not
removed, and the flock/herd
development is very slow
- There is great
variation in transgene
expression between
transgenic individuals
- DNA extracted
for the gene of
interest
- Sperm-Mediated
Gene Transfer
- Demembranated
spermatids are incubated
with the DNA and then
injected into oocytes
- Alternatively, mouse spermatocytes
have been removed, transfected in
culture and transplanted back into
the mouse, making transgenic sperm
- ICSI is
used
- Intra-cytoplasmic
sperm injection
- The egg is held in place
using suction and the
sperm is injected into the
cytoplasm of the egg
- Intra-cytoplasmic
sperm injection
- Alternatively, mouse spermatocytes
have been removed, transfected in
culture and transplanted back into
the mouse, making transgenic sperm
- Sperm
- Cheaper, easier,
less equipment
and skill required
- Cheaper, easier,
less equipment
and skill required
- Spermatids
- More efficient than a
pronuclear injection,
but it is more difficult
to perform ICSI
- More efficient than a
pronuclear injection,
but it is more difficult
to perform ICSI
- Spermatocytes
- Difficult to produce the
transgenic male, but can
then be used in natural
breeding (easier)
- Difficult to produce the
transgenic male, but can
then be used in natural
breeding (easier)
- Genes can only
be added, not
removed, except
for in transfected
spermatocytes
- Random integration
of DNA results in
highly variable
expression of the
transfected DNA
- Generation times of
farm animals are wuite
long, so reliance on
natural breeding is
time consuming
- Generation times of
farm animals are wuite
long, so reliance on
natural breeding is
time consuming
- Random integration
of DNA results in
highly variable
expression of the
transfected DNA
- Demembranated
spermatids are incubated
with the DNA and then
injected into oocytes
- Embryonic
Stem Cells
- Can be kept in
culture almost
indefinitely and so
are useful for
homologous
recombination
- Useful for modelling
human diseases in mice,
looking at gene structure
and function, and to
study cell differentiation
- Mouse ESCs can be
transfected with a
new gene in culture,
micro-injected into a
blastocyst and then
implanted into a
surrogate mouse
- F1 generation are bred
for germline transmission,
creating ES-derived and
non-ES derived offspring
- ES-derived
offspring are bred
to homozygosity
- Results in the
incorporation of
a new gene into
a species
- Results in the
incorporation of
a new gene into
a species
- ES-derived
offspring are bred
to homozygosity
- F1 generation are bred
for germline transmission,
creating ES-derived and
non-ES derived offspring
- Can be kept in
culture almost
indefinitely and so
are useful for
homologous
recombination
- Nuclear
Transfer
- Reconstruction of an
embryo via the transfer
of genetic material from
a donor cell to an
enucleated recipient
egg, from which the
original genetic material
has been removed
- Creates a copy of
the animal the donor
cell came from
- Creates a copy of
the animal the donor
cell came from
- Can be
performed with
embryonic and
somatic cells
- Nucleus is transferred,
de-differentiation occurs
where the somatic genes
are turned off and the
somatic chromatin marks
- All animals
are transgenic
- Allows the first
generation
produced to be
transgenic
- Allows the first
generation
produced to be
transgenic
- Example
- Polly the
sheep
- First transgenic
cloned lamb
- First transgenic
cloned lamb
- Polly the
sheep
- Allows
pre-selection of high
expression cells
- Mammary cells can
be cultured, and a
human gene added
with a marker
- The cell with the highest
expression of the gene of
interest can then be identified
and cloned, before carrying
out nuclear transfer
- The cell with the highest
expression of the gene of
interest can then be identified
and cloned, before carrying
out nuclear transfer
- Mammary cells can
be cultured, and a
human gene added
with a marker
- Reconstruction of an
embryo via the transfer
of genetic material from
a donor cell to an
enucleated recipient
egg, from which the
original genetic material
has been removed
- Pronuclear
Injection
- Transgenic animals can
also be used for producing
antibodies, as an alternative
to bacterial systems
- The animals can be created
to produce high levels of
certain antibodies, which they
then expel in bodily fluids like
blood, milk and urine
- The animals can be created
to produce high levels of
certain antibodies, which they
then expel in bodily fluids like
blood, milk and urine
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