2. Extraction of DNA
DNA is found within nucleus of all eukaryotic
cells
Extraction is not difficult. Cells are broken apart
to release cellular contents. Addition of
detergents will breakdown nuclear membrane
to release DNA.
Alcohol is added, enabling DNA to settle before
purification and extraction takes place.
3. Genetic Engineering / Modification
Is the isolation and manipulation of genes
extracted from DNA of species
Involves taking genes from one organism and
transferring them to another species or putting
them back into the original organism in an
altered state.
4. Uses of Genetic Engineering
- Produce desired proteins like insulin or
vaccines
- Improving plants: pest resistant cotton,
increased viral resistance, increased nutrition
- Improving animals: improved wool or milk
production, improved meat; transgenic pigs
etc.
- Selective breeding
5. Gene probes
Gene probes are single stranded DNA or mRNA
segments that have been constructed or man-
made. They have specific radioactive or
fluorescent markers that enable them to be
traced.
These probes work by binding in a
complementary manner to the “gene of
interest” and in the process identifying the
location of the gene on the chromosome
8. Restriction Enzymes
Restriction enzymes such as Escheria coli
(EcoR1) are naturally occurring enzymes found
in organisms like bacteria that enable specific
DNA nucleotide sequences (4-8) to be
recognised and cut in specific locations
These enzymes cut DNA molecules above and
below a “gene of interest” for extraction and use
in genetic engineering.
9. An incision is made through the sugar-phosphate
backbone, leaving “sticky ends” either side which
have exposed bases that have use in
complementary binding during genetic
manipulation.
DNA can be cut many times by the one restriction
enzyme – these fragments called “restriction
fragments”
12. Transgenic Organisms
Organisms which have genetic information
incorporated into the genome of another
organism.
Plants
Sections of DNA from bacteria called plasmids to
introduce new genes into plants.
Plasmids are circular pieces of DNA or RNA
found in bacteria and yeast.
13. They have 3-200 genes, often coding for such
features such as resistance to antibiotics
Using restriction enzymes, a gene of interest
(e.g. herbicide resistance) is cut from one
species and inserted using ligase enzymes into
the plasmid. They are then integrated into the
plants chromosomes.
The recombinant cell is cultured to grow into a
new genetically engineered plant.
E.g. Agrobacterium
16. Other methods of gene transfer into pants
include
Electroporation
An electrical pulse method in which DNA is
delivered directly into cells
Micro particle gene gun used to fire DNA on
inert molecules (gold or tungsten) into cell
where transcription can take place.
17. Animals
Transfer of genes into animals involves three
steps
1. Isolation and extraction of specific gene by
the use of restriction enzymes.
2. Injection of the recombinant DNA with a fine
glass needle into the pro nuclei of an
embryo, 12-24 hours after fertilization.
3. Transfer the embryo to a recipient mother
where it can grow and develop into a
transgenic animal.
19. The cloning of genes is performed using host
bacteria (EcoR1)
Viral factors
A virus consists of genetic material combined with
protein. They can only reproduce inside a host
organism that they infect.
Scientists use viral particles as vectors to transmit
information by attaching a required gene to the
genome of the virus and then engineering the
infection of particular tissues.
E.g. Cold virus as vector in treating cystic fibrosis, a
disease involving excess mucous production
20. Human Genetic Engineering
Polymerase Chain Reaction (PCR)
The multiplication or amplification of amounts of
DNA for testing. Three steps are involved
1. Required DNA is added to a test tube and
heated to about 950 to separate two
complementary strands. Primers are used to
prevent strands re-joining and also limit copied
sequences to about 400 bases to reduce errors
2. DNA replication enzyme DNA polymerase is
added along with free nucleotides. Heat tolerant
enzyme from bacteria is used to allow
temperature to be raised.
21. 3. DNA is cooled to allow binding of free
nucleotides to exposed bases and formation of
complementary strand
Each time the replication occurs the mount of DNA
is doubled.
20 PCR cycles an produce a million DNA
This DNA can be used for
Evolution research
Analysing DNA from preserved fossils
Rapid pre-natal diagnosis
Amplifying DNA from crime scenes
22.
23. Electrophoresis
Restriction segments are placed at one end of
gel. Positive and negative electrodes are
attached to the gel. The phosphate groups on
the DNA molecule give it a negative charge and
consequently fragments move to the positive
end.
Smaller segments move faster than longer ones.
Electrophoresis helps separate DNA according to
size and charge
25. DNA Sequencing
Technique used to work out sequence of
nucleotide bases in a DNA strand
Using PCR, Fred Sanger 1960’s devised a way of
stopping DNA replication at particular known
end points creating a collection of DNA
fragments of different sizes.
They were then separated into four columns
according to their known base end
27. DNA Finger Printing
As human tissue (hair, saliva, skin, blood,
semen) can be left at a crime scene,
theoretically it is possible to identify the
individual involved by using
electrophoresis and DNA sequencing and
creating autoradiographs.
These autoradiographs indicate a band
pattern of an individuals DNA or their DNA
fingerprint
28. DNA Finger Printing
An advantage over the use of fingerprints and
blood typing is that DNA lasts a long time (3-4
years)
Technique relies on fact that eukaryotic
organisms a have a higher proportion of DNA
which has no function -“junk DNA”
This DNA has highly repetitive sequences of
bases and the number of time it is repeated is
unique to an individual organism
29. These repeated sections are called
“microsatellites”
These repeated sections are digested by
restriction enzymes they form Restriction
Fragment Length Polymorphisms (RFLP)
These RFLP’s are separated by electrophoresis to
create a unique pattern for comparison with other
known sequences called DNA profiling
32. Social Consequences
Positives?
Scientists believe that the risks associated with
genetic engineering are minimal.
DNA is transferred in a controlled fashion and
with incorporation of only specific genes
Negatives?
There is a fear that transferring genes may
create pathogenic or dangerous species.
Other social or ethical considerations?
33. Factors for consideration before
genetic modification can be approved
The reasons for use
The characteristics of the DNA transferred
Effects of modified organism on people, plants
and animals
Effect on natural habitat
Possible interbreeding with other organisms.
34. Areas of Concern
Individuals within species become too similar,
resistance to disease can be lost
Consideration may be given to people cloning
themselves to provide organs for he future
Billions of years of evolution is tampered with
within a relative short span of time
Profit and industrial growth may be to the
detriment of ecosystem and the biosphere
(GM foods)
Ones genes may be used “against” them
(Ethical considerations)
