IB Genetics Topic 4:
Genetic Engineering
Topics in Genetic Engineering
• Polymerase Chain Reaction (PCR)
• Gel electrophoresis
• DNA profiling
• The genome project
• Gene transfer
• Genetic modification in plants and animals
• Cloning
We will be brief!
• The Blog has videos and games for you to
cement your understanding of each topic!
4.4.1: The Polymerase Chain Reaction
• Kary Mullis, 1984,
Nobel Prize 1993
• ‘Reviewers and
Biographers often
latch on to his
enjoyment of drugs,
womanising and
surfing to paint him
as some sort of cool
rock star
rebel…but…’
What does PCR do?
• It quickly amplifies a tiny
sample of DNA into
millions of identical
copies
• This produces enough
DNA to allow further
analysis and study.
The DNA sequences amplified by PCR
are used for:
• Forensic identification - crime
(CSI….)
• Paternity suits
• The Genome project: determination
of the entire human genetic code
• Diagnosing diseases and genetic
disorders – genotype analysis
• Detection of bacteria and viruses in
the environment
• Evolutionary research
How does PCR work?
First, you need to extract DNA from
cells.
Next, PCR requires:
• Custom-made DNA primers
• (TAQ) DNA polymerase
• Nucleotides for complementary
base pairing
• HEATING and COOLING:
Thermocycler machine
PCR can produce 100 billion copies of
the DNA sample in a few hours
Let’s do it!
• PCR the movie
• PCR the cartoon
• PCR the game
4.4.2: Gel electrophoresis
1.
2.
3.
4.
5.
6.
Commonly the DNA sample is first amplified
by PCR
The DNA sample is chopped into fragments
using restriction enzymes
Gel electrophoresis separates fragments of
DNA according to their size
DNA samples are placed in a gel, fluorescent
marker added (tag attached to a triplet), and
an electric charge is applied to push
fragments along
The shortest fragments travel furthest
through the gel, while the longest (heaviest)
remain closer to their origin
This lets us ‘match’ the sample against
another DNA sample or standard
Let’s do it!
• Virtual Lab 1
• Virtual lab
4.4.3: DNA profiling
•
•
•
•
HOW?
DNA sample (blood, semen,
cheek swab)
Sample is amplified by PCR,
then matched against known
samples using gel
electrophoresis
We look for standard tandem
repeating DNA: highly
repetitive sequences from
non-coding region of DNA
STR’s are unique to
individuals
APPLICATIONS
Numerous techniques for
DNA profiling:
• Criminal forensics
• Paternity suits
• Ecology – identifying
relationships in
migrating birds, whales
etc
• Evolutionary genetics
Famous examples of DNA profiling
• The innocence project
• The famous blue dress
• Identifying the Mona
Lisa
• Identifying the
Romanovs
DNA profiling: paternity and forensics
• The fluorescent banding
pattern shows up for
each DNA fragment and
can be compared with
test/ known sample
• Usually >4 ‘STR’ sites
are used to establish
paternity or identity
4.4.6: The Human Genome project
• We’re all the same!
• We’re all different!
• Welcome to the human genome
Started in 1990, first draft published in 2003,
ongoing refinement…
Amazing international effort
• The BBC tell us about the genome 10 years on
• Hank tells us some surprises about the human genome
project
• ..so what has the human genome project achieved, so
far?
Key outcomes of the Human Genome
project
• We identified the number (30,000) and loci of all the genes
of our genome
1. Human health: Medical diagnostics, treatments,
pharmacogenomics, gene therapy
• We identified many new proteins and their functions
2. Transgenics: move production of beneficial proteins from
one species to another, design novel proteins
• We compared human DNA with that of other species
3. Evolutionary genetics and evolutionary history
4. Bio-informatics: Genetic databases and the bio-informatics
industry
The HGP and human health
• 2 out of 3 of us will die
of a genetically related
disease
• Many (some say all)
diseases have a genetic
cause
• Genetic report cards
can identify ‘potential
risk’ of future illnesses
• The future is here...
Do you want to know your genome?
• Do you want to
know your genome?
• Are you sure?
The human genome and new medicine
(1): Gene therapy
• Find defective genes
and ‘fix them’
• Insert a healthy normal
gene or gene product
(lipid, protein)to
achieve normal function
• Most effective for single
gene disorders: cystic
fibrosis, Sickle Cell
disease,
• gene therapy in depth
• A lucrative business...
The human genome provides
avenues for new medicines
• Identify beneficial molecules which are
produced in healthy people
• Identify the gene which produces the
desirable molecule
• Copy that gene and use it as a recipe to
synthesise the molecule in a laboratory (or in
another organism!)
• Distribute the beneficial molecule as a new
treatment
The HGP and medicine (3):
Pharmacogenomics
Uses information about
your genetic make-up to
determine the drug, and
drug doses, that will
work best for you
Currently used for
treatment of:
• HIV
• Breast cancer
• Colon cancer
• Mental illness
more info here...
3. Using the HGP to understand human
evolution
By sequencing and databasing
genes, we can see similarities and
differences between species
• The closer the genome match,
the closer their evolutionary
history
• Human Chromosome 2 came
from fusion of two great ape
chromosomes
• Karl Miller on human evolution
• The time-tree of evolution
Ethics and the human genome
How companies are
patenting your genetic
code
4.4.8: GENETIC ENGINEERING,
(MODIFICATION, TRANSGENICS)
BIOTECHNOLOGY
The basic premise for genetic
engineering…
The genetic code is universal
• All living things share the same code
• Each codon codes for the same animo aacid,
regardless of the species
• Genes can be transferred from species to
species, to produce the same product
We can cut, copy and paste DNA between
species
Gene transfer 101: the basics of cutting,
copying, pasting and cloning genes
• An introduction
• Step-by-step
How does genetic engineering work?
1. Cut out desired DNA
using restriction
endonuclease
2. Prepare plasmid using
the same restriction
enzyme
3. Insert DNA into
plasmid using DNA
ligase
4. Insert plasmid (vector)
into host cell
Applied gene transfer: Gene Therapy
Gene therapy for treatment of Severe Combined
Immunodeficiency Disease
(2)
Genetic Engineering: Making Human
insulin
• E. Coli make human insulin
Genetic Engineering: Making Factor IX
in sheep…
1997: Factor IX isolated and purified from sheep’s milk
to treat one hereditary form of haemophilia (Haemophilia B,
Christmas Disease)
Polly and Molly the Factor IX sheep
Transgenic (GM) plants
Conferred Trait
Organism
Genetic change
Herbicide resistance
Soybean
‘Roundup’: Glysophate
resistance
Flavr Savr
Tomato
Switch off gene for
ripening – delays natural
softening, improves
flavour
Insect Resistance
Bt Corn
Resistance to European
corn borer introduced by
addition of toxin from
Bacillus Thuringiensis
Salt-resistance
Tomato
Extended range for tomato
production
Beta carotene
‘Golden rice’
Protection against betacarotene deficiency
Transgenic plants: The controversies…
The controversies….
Transgenic (GM) animals
Conferred Trait
Sheep
Genetic change
Fluorescence
(gfp gene)
Fish (pigs, cats)
Fluorescence
used as
biosensor for
other
transferred
genes
Factor IX
production
Sheep
Production of
Factor IX in
milk for
haemophilia
Milk quality
Cows
Milk equivalent
to human milk
Glowing animals?....what’s the big
deal?
Worth a Nobel prize….
Further Applications of Transgenic
Technology
• Vaccines (transgenic yeast produces vaccine
for Hepatitis B)
• Transgenic mice widely used for human
disease research
• Transgenic male mosquitoes carrying ‘lethal
gene’ used to reduce the incidence of Dengue
fever
Genetic modification: the PROs…
• GM crops should improve yields,
quality and food security
• Pest-resistant crops will reduce the
need for pesticides
• GM can produce crops which provide
dietary supplements such as retinol
• GMO’s used to produce rare proteins
for medicine or vaccines will be
cheaper and less polluting than
conventional methods
• GM allows farmers greater control
for selective breeding of crops and
animals
Genetic modification: the CONs…
• No one knows the long-term effects of GMO’s in the
biosphere PRECAUTIONARY PRINCIPLE
• Genes from GM crops are easily integrated into the wild
type crop
• Genes may be able to cross species
• Crops which produce toxins to kill insects could prove toxic
to humans
• Large portions of the human food supply may fall under the
control of a small number of companies
• High-tech agricultural ones are not necessarily better than
simpler solutions
• A proliferation of GMO’s could drastically reduce natural
biodiversity
Where do you stand?
4.4.11: CLONING
What is a clone?
• A group of genetically identical organisms
• A group of cells artificially derived from a
single parent
Natural Clones
• Asexual reproduction:
bacteria, yeasts,
protozoa
• Vegetative propagation
in plants
• Monozygotic (identical)
twins
4.4.12: ‘Outline a
technique for cloning
using differentiated
animal cells’
4.4.13: THERAPEUTIC
CLONING: Somatic cell
nuclear transfer
Therapeutic cloning
Ethical issues surrounding therapeutic
cloning
• Therapeutic cloning allows
production of embryonic
stem cells from
differentiated cells
• These embryonic stem cells
have great potential for a
patient to replace their own
damaged cells - skin, heart,
kidney, brain, etc etc.
• A promising technique of
stem cell production
• These embryonic stem cells
have the potential to
become a human being (so
called reproductive cloning)
• Reproductive cloning of
humans is illegal in most
countries
Therapeutic cloning is
aimed NOT at making
people, but at CURING
people
Therapeutic cloning: The controversies
1. New potential therapies
for disease
2. Production of immunocompatible tissue for
self-transplantation
3. Advances in medical
research
4. Cost-benefit firmly in
favour of therapeutic
cloning
1. Manipulation and
destruction of human
embryos is wrong
2. Reproductive cloning
becomes more likely
3. We will create a global
market for women’s
eggs