In Principle: Genetic Engineering involves the laboratory
manipulation of DNA What does a particular
region of DNA
do?
Isolation & manipulation of "gene of interest"
Sources of DNA fresh viral, prokaryotic, or eukaryotic (plant &
animal, etc.) DNAseparated from other molecules by selective binding
(CSHL animation
of DNA extraction)
Ancient DNA (aDNA)
museum specimens: 10s ~ 100s years fossils: 1,000s ~ 1,000,000s years Ex.: insects in amber Ex.: ancient humans: Neanderthals, Denisovans, &
relatives
Forensic DNA Forensics:
data used as evidence Ex.: blood/ semen stains at crime scenes Ex.: What species do
thesefillets come from?
Environmental DNA (eDNA)
Ex.: What taxa (prokaryotic phyla
or eukaryotic species) present?
Marine, freshwater, terrestrial monitoring
In vivo Molecular
Cloning of DNA
Type-II restriction endonucleases
cut DNA only at specific restriction (recognition) sites
(list) DNA
palindrome -
"Able was I ere I saw Elba"
"Madam, I'm Adam"
"A man, a plan, a canal:
Panama!"
"Straw? No!
Too stupid a fad, I put soot on warts."
''Doc, note
I dissent. A fast never prevents a fatness. I diet on cod."
"Saippuakivikauppias" - 15-letter Finnish word for
a soap seller restriction
site reads the same in 5'3' direction on both strands
Overhanging TTAA-5' are "sticky ends"
Vector insertion Vector - a means of moving DNA
from one place to another Plasmids - a circular,
extrachromosomal DNA
"naked DNA", "bacterial virus" pUC18
- an artificial plasmidwith: selectable markers that tell you when
plasmid is present antibiotic
resistant (e.g., tetracycline or ampicillin)
lacZ
gene produces beta-galactosidase,
metabolizes (unusual) Xgal sugar blue product lacZ gene
includes polylinker
multiple, unique restriction sites
Recombinant DNA
molecules formed when linearization
of vector DNA by digestion with endonuclease ligation
of "sticky ends" between source DNA & vector DNA
re-combines DNA from two
different sources In vivo cloning in E.
coli E. coli K12strain can't grow in presence
of antibiotics (antibiotic-sensitive) can't metabolize X-galactose (Xgal)
sugars Host transformation
integrates plasmid DNA into bacterial chromosome Bacterium
acquires genes from plasmid, including "Gene of Interest" Colony Selection Scheme:
finding rare bacterium with recombinant DNA Only E. coli cells with resistant plasmids grow on antibiotic medium; only
plasmids with functional
lacZ gene can metabolize Xgal lacZ(+)blue colonies lacZ functional polylinker intact nothing inserted, no clone lacZ(-)white colonies
polylinker disrupts
lacZsuccessful insertion
&recombination
!
Bulk
bacterial culture of recombinant(white)
colonies
Purify cloned plasmid DNA, cut cloned gene out with
endonucleases: Gene of Interest ready for Analysis
Polymerase
Chain Reaction
In vitroDNA "cloning": "DNA
xeroxing" w/ four components & gadget
DNA template
anything with DNA in it
oligonucleotide primers ("oligos") short (20 ~ 30 base) ssDNA complementary to
gene of interest
some knowledge of gene is required :
"Universal primers" work across many species
Taq
DNA polymerase
heat-stable enzyme from hot-spring bacteria (Thermus aquaticus)
functional at 70 ~ 80oC, withstands
exposure to 95oC dNTPs: four building-blocks
for DNA
Thermal cycler: computer-controlled heating
& cooling block
temperature change > 1oC / sec
PCR doubles
gene copy number each cycle denature
/ anneal / extend: 2 4 8 16 32 64 etc.:
10 cycles = 210
= 103 copies, 20 cycles 106
copies,30 cycles
109 copies
[
of PCR]
Thermal cycler
automates
process replicates specific gene
segment only sufficient [DNA]for direct analysis
Variations: quantitative
PCR (qPCR)
cf.
qualitative (preparative) PCR
produces DNA in bulk quantitative (analytical) PCR rxns
monitored in "real time"
Laboratory exercise in PCR primer design Analysis of
cloned and (or) PCR-amplified DNA
Automated DNA sequencers
uses laser fluorometry ddNTPs
attached to fluorescent dyes in single reaction scanning laser activates & fluorometer "see"
fluorescence colours (A C G T) [HOMEWORK]
computer "calls
sequence" as chromatogram
( of automated DNA sequencing)
Next
Generation sequencing uses massively-parallel,
high-throughputmethods
NextGen sequencers use capillary separation,
other methods
Southern Blot
analysis
Useful when gene of interest rare: one locus / genome DNA transferred ("blotted")
to filter paper Filter
exposed
to a DNA probe Probe: instrument or method that measures something (e.g.,
thermometer) ssDNA
complementary to gene region of interest
~ same as primer /
oligo in PCR
experiment
Binds specifically to target DNA immobilized on filter Radioactive label with 32P-dNTPs exposes X-ray
film Autoradiogram shows presence / absence
& size of
target DNA RFLP
differences