GENEtIc ENGINEERING - Midstream

mustardnimbleΒιοτεχνολογία

11 Δεκ 2012 (πριν από 4 χρόνια και 11 μήνες)

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Genetic Engineering
An iconic image of genetic engineering;
this 1986 "autoluminograph" of a glowing
transgenic
tobacco
plant bearing the
luciferase
gene of
fireflys
strikingly
demonstrates the power and potential of
genetic manipulation.
Changing the Living World
A.
Selective Breeding
Selective Breeding

the deliberate breeding
of organisms to
produce certain desired traits
which crosses
consists of
Selective
Breeding
for
example
Inbreeding
Hybridization
(aka
outbreeding)
Similar
organisms
Dissimilar
organisms
for
example
Organism
breed A
Organism
breed A
Organism
breed B
Retains desired
characteristics
Combines desired
characteristics
which
which crosses
which
Section 13
-
1
Concept Map
1.
Inbreeding
Inbreeding

crossing (breeding) of
organisms that have a
similar genotype
(often closely related)
+
Within a few generations,
offspring
are homozygous
for desired traits
-
Offspring can
also carry undesired
traits
ex: pitbulls w/ underbite,
German shepherds with hip
dysplasia
2.
Hybridization
(aka Outbreeding)
-
crossing of
distantly related organisms
Combine positive
desired traits of both
species
Hybrid vigor

hybrids are sometimes
stronger and hardier
than parents.
Hybrids are
often sterile
(unable to
reproduce
+
-
+
=
Manipulating DNA
A.
The Tools of Molecular Biology
Scientists
use their knowledge
of the structure of DNA and
its chemical properties to
study and change DNA
. Different
techniques are used to :

Extract DNA
from cells

Cut DNA into
smaller pieces

Identify the sequence
of bases in a DNA molecule

Make unlimited
copies
of DNA
These are all examples of
genetic engineering

any
technique used to
identify or change genes
at the molecular
level
1.
DNA Extraction
How is DNA taken out of
a cell? It’s pretty simple

you did it in the recent
lab! Chemicals are used
to
open the cell
(using
detergents) and the
DNA
is separated out
from
other cell parts (using
ethanol).
2.
Cutting DNA
Most DNA molecules are very large, so scientists cut
them into smaller pieces using
restriction enzymes.
There are hundreds of them, and each
cuts DNA at a
very precise place.
Recognition sequences
DNA sequence
Recognition sequences
DNA sequence
Restriction enzyme
EcoR
I
cuts the DNA
into fragments.
Sticky end
Section 13
-
2
Restriction Enzymes
3.
Separating DNA
Gel electro
phore
sis

a process used to
sort DNA
―phore‖ = move molecules
by size
DNA plus restriction
enzyme
Power source
Mixture of DNA
fragments
Gel
Longer
fragments
Shorter
fragments
1.
Reading the Sequence

scientists figure out the
sequence of an unknown strand by
synthesizing a copy
using dyed bases
. The order of the colored bands
indicates the base sequence.
Figure 13
-
7 DNA Sequencing
B.
Using the DNA Sequence
2.
Cutting and Pasting
DNA sequences can be changed by
adding in gene
sequences taken from a different organism. This is
known as
recombinant DNA

DNA with
components
from different organisms
.
DNA polymerase adds
complementary strand
DNA heated to
separate strands
DNA fragment
to be copied
PCR
cycles 1
DNA
copies 1
2
2
3
4
4
8
5 etc.
16 etc.
Section 13
-
2
Figure 13
-
8 PCR
In order to
study genes,
scientists often
like to have
many copies
of
a gene. The
technique of
polymerase
chain reaction
(PCR)
helps
biologists to do
that.
Sneaking In
You probably have heard of computer viruses.
Once inside a computer, these programs follow
their original instructions and override instructions
already in the host computer. Scientists use small
―packages‖ of DNA to sneak a new gene into a cell,
much as a computer virus sneaks into a computer.
Section 13
-
3
Interest Grabber
13

3
Cell Transformation
This is called
transformation
.
During transformation,
a
cell takes in DNA from outside
the cell. This
external DNA becomes a component of the cell’s
DNA.
Recombinant DNA
Flanking sequences
match host
Host Cell DNA
Target gene
Recombinant DNA replaces
target gene
Modified Host Cell DNA
Section 13
-
3
Knockout Genes
Human Cell
Gene for human
growth hormone
Recombinant
DNA
Gene for human
growth hormone
Sticky
ends
DNA
recombination
DNA
insertion
Bacterial Cell
Plasmid
Bacterial
chromosome
Bacterial cell for
containing gene for
human growth hormone
Section 13
-
3
Figure 13
-
9 Making Recombinant DNA
This is accomplished using
vectors
, a
carrier of genetic
material
. Commonly used vectors are viruses and
plasmids
, small
circular pieces of bacterial DNA.
Plasmids often have
genetic markers
, special
genes used
to identify
the transformed bacteria.
The Good With the Bad
The manipulation of DNA
allows scientists to do some
interesting things. Scientists
have developed many
transgenic organisms
, which
are
organisms that contain
genes from other organisms
.
Recently, scientists have
removed a gene for green
fluorescent protein from a
jellyfish and tried to insert it
into a rabbit. (Rabbit is named
Alba, seen here under UV
light.)
Section 13
-
4
Intere
Applications of Genetic Engineering
A.
Transgenic Organisms
1.
Transgenic Microorganisms
Transgenic bacteria now
produce many
substances
that are important
for health or industry
:

Insulin

Growth hormone

Clotting factor

Cancer fighting substances

Raw materials for plastics and synthetic
fibers

Bacteria able to digest oils or other toxic
chemicals
2.
Transgenic Animals
Transgenic animals are used to
study genes
and to improve
food supply
.

Mice with immune systems similar to human immune
system (to
study diseases
)

Livestock with extra copies of growth hormone genes
(
grow faster
and with leaner meat)
3. Transgenic Plants
Transgenic plants are an important part of our food supply:

In 2000,
52% of
soybeans
and
25% of corn grown
in U.S.A.
was genetically modified (GM) to be
resistant to weed
-
killing
chemicals. This allows them to survive when a crop is sprayed
with weed
-
killer.
A donor cell is taken from
a sheep’s udder.
Donor
Nucleus
These two cells are fused
using an electric shock.
Fused Cell
The fused cell
begins dividing
normally.
Embryo
The embryo is placed
in the uterus of a foster
mother.
Foster
Mother
The embryo
develops normally
into a lamb

Dolly
Cloned Lamb
Egg Cell
An egg cell is taken
from an adult
female sheep.
The nucleus of the
egg cell is removed.
Section 13
-
4
Figure 13
-
13 Cloning of the First Mammal
B.
Cloning
A
clone
is a member of a population of
genetically
identical cells all produced from a single cell
. This is
easy to do with bacteria, not so easy with multicellular
organisms. Dolly was produced in 1997 by Scottish
scientist Ian Wilmut.
Cloning
Section 13
-
4
Flowchart
A body cell is taken from a donor animal.
An egg cell is taken from a donor animal.
The fused cell begins dividing, becoming an embryo.
The nucleus is removed from the egg.
The body cell and egg are fused by electric shock.
The embryo is implanted into the uterus of a foster mother.
The embryo develops into a cloned animal.
Bioethics
Bioethics
is the study of the
ethical and moral
implications
of new biological discoveries and biomedical
advances.
While much of our genetic engineering work has many
exciting ideas involved, there are also serious
considerations. For example, studies have shown that
cloned animals may suffer from a number of genetic
defects and health problems. Many people oppose such
work. Are we willing to consider these problems in the
cloning of humans?
As these techniques improve, these issues will become
more pressing, and will need to be decided by YOU.