1. PROFESOR DR HJH FARIDA
ZURAINA MOHD YUSOF
Dean of FSG
ADVANCED MOLECULAR BIOLOGY
TECHNIQUES [OVERVIEW & TOOLS]
2. 1. Overview of Recombinant DNA technologies
a. Injection of DNA or a nucleus into a cell
b. Gene Therapy
c. “Pharm” Animals
d. Genetic Modification of Plants (e.g. GM foods)
e. Use of Prokaryotes to produce Eukaryotic gene products
3. Injection of DNA or a nucleus into Cell
Potential Applications
1. Germ line Gene Therapy—inject therapeutic gene into an egg cell (affects future generations)
2. Somatic Gene Therapy—Inject therapeutic gene into a somatic cell, culture & reinsert into an
individual
3. Cloning—inject nucleus into an enucleated egg, culture & implant into a surrogate mother.
Drawback: Inefficient means of gene transfer
4. Use of a Retrovirus
for Gene Therapy
Applications
Somatic Gene Therapy to treat
• Gaucher Disease
• SCID’s “Bubble Boy”
(Severe Combined Immune Difficiency)
5. Transgenic “Pharm” animals
Potential Applications
• Genetically modify mammals to
produce therapeutic peptide
drugs (e.g. insulin, )
• Isolate and purify drug from the
milk
• Potentially a more cost effective
method to produce
pharmaceuticals
6. Using the Ti plasmid as a vector for genetic engineering in plants
Potential Applications
Genetically modify plants to...
• produce vaccines in their fruit (e.g. polio vaccine)
• be resistant to disease and pests
• require less fertilizer, pesticides and herbicides
• have a higher nutritional value
7. “Golden” rice contrasted with ordinary rice
Transgenic Rice
• Genetically modify plants to produce beta-carotene
• Beta Carotene is converted to vitamin A in humans
• Vitamin A deficiency leads to poor vision and high susceptibility to disease
~70% of children <5 years old in SE Asia suffer from vit. A deficiency
8. Figure 20.2 An overview of how bacterial plasmids are used to clone genes
9. 2. Overview of various techniques
a. Use of Restriction Enzymes & DNA Ligase to make
recombinant DNA molecules
b. Use of Gel Electrophoresis...
• To separate restriction fragments
• For DNA fingerprinting
c. PCR (Polymerase Chain Reaction)
10. Using a restriction enzyme and DNA
ligase to make recombinant DNA
Figure 20.3
11. Gel Electrophoresis
1. A method of separating mixtures of large molecules
(such as DNA fragments or proteins) on the basis of
molecular size and charge.
2. How it’s done
• An electric current is passed through a gel containing the
mixture
• Molecules travel through the medium at a different rates
according to size and electrical charge:
Rate a size and charge
• Agarose and polyacrylamide gels are the media commonly
used for electrophoresis of proteins and nucleic acids.
15. PCR—Polymerase Chain Reaction
• A very quick, easy, automated method used to
make copies of a specific segment of DNA
• What’s needed….
1. DNA primers that “bracket” the desired sequence to be
cloned
2. Heat-resistant DNA polymerase
3. DNA nucleotides
4. Thermocycler
17. 3. Strategies used to Genetically Engineer Bacteria
See fig. 20.2. An overview of how bacterial plasmids are used to clone genes
1. Isolate the gene of interest (e.g. insulin gene)
2. Insert the gene of interest into a bacterial R-plasmid
• R-plasmids are circular DNA molecules found in some
bacteria that provide resistance to up to 10 different
antibiotics
3. Place the transgenic plasmid into bacterial cells
• Plasmid DNA reproduces each time the bacteria reproduce
4. Culture the bacteria and isolate the gene product (e.g.
insulin)
18. 3. Overview of how bacterial plasmids are used to clone genes
Figure 20.2
19. Step 1. How to Isolate the Gene of Interest
Use Reverse Transcriptase to make the gene of Interest
Method #1 (see figure on next slide)
1. Isolate mRNA for the gene product of interest (e.g. Insulin
mRNA)
2. Use Reverse Transcriptase to produce cDNA (complementary
DNA)
3. Use PCR to clone the cDNA
3. Separate the synthetic gene of interest by electrophoresis
20. Use of Reverse Transcriptase
to make complementary DNA
(cDNA) of a eukaryotic gene
21. Step 1. How to Isolate the Gene of Interest
Use Reverse Transcriptase to make the gene of Interest
Method #2
1. Determine the primary structure (i.e. the amino acid sequence)
of the protein of interest (e.g. insulin) with an automated protein
sequencer
2. Use table of codons to determine the mRNA sequence
3. Synthesize the mRNA in the lab
4. Use Reverse Transcriptase to produce cDNA and PCR to
clone the cDNA (as before)
5. Separate the synthetic gene of interest by electrophoresis
22. 1. How to Isolate the Gene of Interest
Use a labeled DNA Probe to Isolate Gene of Interest (Southern Blot Method see next slide)
1. Extract and purify DNA from cells
2. Cut DNA with restriction enzyme (e.g. Eco R1)
What’s a restriction enzyme? (fig. 20.3)
Note: Must cut outside of gene w/o too much “excess baggage”
3. Separate DNA fragments by gel electrophoresis
4. Transfer DNA from the fragile gel to a nylon sheet and heat to sep. strands (fig. 20.10)
5. Hybridize gene of interest with a radio-labeled DNA* or mRNA* probe and expose w/
film to locate gene
How do these probes work? (fig. 20.10)
6. Use PCR to clone the isolated gene of interest.
24. Steps 2 & 3. How to Insert the Gene of Interest into the R-Plasmid
See next 3 figures and animation
• Lyse bacteria with detergent to release the R-plasmid (e.g. ampicillin resistance plasmid)
• Cut the plasmid with the same restriction enzyme used to isolate the gene of interest
3. Mix plasmid with gene of interest and join the two with DNA ligase
How does this work?
4. Add the recombinant plasmid to a bacterial culture
Induce bacteria to take up plasmid (transformation)
5. Grow bacteria on agar plate containing an antibiotic (e.g. ampicillin)
6. Isolate those bacterial colonies that contain the recombinant plasmid How?
Only some of the bacteria take up a plasmid—How do you know which ones did?
Not all plasmids are recombinant plasmids—How do you find those that are?
Only some of plasmids contain the gene of interest—How do you identify these?
26. Using Plasmids to Create Recombinant DNA
1. Digest a plasmid vector with a restriction enzyme (e.g.
EcoRI) at a single site to produce two sticky ends.
2. Digest human DNA with EcoRI to produce pieces with the
same sticky ends
• Use Human DNA or cDNA copied from mRNA using reverse
transcriptase from retroviruses.
3. Mix the two samples and allow to hybridize.
• Some plasmids will hybridize with pieces of human DNA at the
EcoRI site.
4. Use DNA ligase is used to covalently link the fragments.
27. Insertion of Recombinant Plasmids into Prokaryotic Cells
1. Only some of the bacteria take
up a plasmid—How do you
know which ones did?
2. Not all plasmids are
recombinant plasmids—How
do you find those that are?
3. Only some of plasmids contain
the gene of interest—How do
you identify these?
28. Identification of cells containing plasmids
• Cells containing plasmids contain the ampicillin
resistance gene
• Grow cells on medium containing ampicillin
• How do you know which colonies contain the gene of
interest?
• Use a DNA probe (see fig. 20.5)
29. Figure 20.5
Using a DNA probe to
identify a cloned gene in a
population of bacteria
30. Step 4. Culture Bacteria and Isolate Gene Product
• Grow the recombinant bacteria in nutrient broth
and isolate/purify the gene product from the broth
• Expensive to do, therefore mammals (e.g. cows and
goats) are now being genetically modified to
produce desired gene products in their milk!!
31. Human Gene Therapy using...
a. Retroviruses
b. Adenoviruses
c. Liposomes
d. Naked DNA
32. Use of a Retrovirus
for Gene Therapy
Applications
Somatic Gene Therapy to treat
• Gaucher Disease
• SCID’s “Bubble Boy”
(Severe Combined Immune Difficiency)
33. Basic Strategies of Human Gene Therapy (1 of 2)
1. Isolate and then clone the normal allele by PCR
2. Insert normal allele into a disabled virus
• Retroviruses and adenoviruses are the most common vectors
• Retroviruses are much more efficient at forming a provirus, but have a
greater chance of mutating to cause disease
• Adenoviruses are safer, but are relatively inefficient as a vector
• Liposomes (lipid spheres) are also used as vectors
e.g. Gene therapy for Cystic Fibrosis involves using an inhaler to bring
liposomes containing the CFTR gene to the cells lining the lungs)
3. Infect host cells with recombinant virus
34. 3. Infect host cells with recombinant virus
a. Add recombinant virus directly to individual
e.g. Jesse Gelsinger—
Had Ornithine Transcarbamylase Deficiency; Causes build
up of ammonia in liver cells since they cannot convert the
ammonia (toxic) produced by amino acid metabolism to
urea (less toxic)
Died in Sept.’99 due to a severe immune response to the
genetically modified adenovirus containing the OTC gene
b. Isolate host cells from body and then add recombinant virus
(e.g. blood stem cells in gene therapy for Gaucher disease)
• Inject genetically engineered cells back into the body
Basic Strategies of Human Gene Therapy (2 of 2)
![PROFESOR DR HJH FARIDA
ZURAINA MOHD YUSOF
Dean of FSG
ADVANCED MOLECULAR BIOLOGY
TECHNIQUES [OVERVIEW & TOOLS]](https://image.slidesharecdn.com/advancedbiotechnology-230203082258-00b4c853/85/Advanced-Biotechnology-ppt-1-320.jpg)
