Quickie Intro to
DNA Technologies
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2006-2007
Watson and Crick
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1953 article in Nature
Double helix structure of DNA
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Cut DNA
 Restriction enzymes
restriction endonucleases
 discovered in 1960s
 evolved in bacteria to cut up foreign DNA

 “restriction”
 protection against viruses & other bacteria
 bacteria protect their own
DNA chemically & by not
using the base sequences
recognized by the enzymes
in their own DNA
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1960s | 1978
Discovery of restriction enzymes
Werner Arber
Daniel Nathans
Restriction enzymes are
named for the organism
they come from:
EcoR1 = 1st restriction
enzyme found in E. coli
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Restriction
enzyme movie
Hamilton O. Smith
Restriction enzymes
 Action of enzyme
cut DNA at specific sequences
 restriction site
 sticky ends
 Many different enzymes

CTG|AATTCCG
GACTTAA|GGC
named after organism they are found in
 EcoR1, HindIII, BamH1, Sma1
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
symmetrical “palindrome”
 produces protruding ends

CTGAATTCCG
GACTTAAGGC


Madam I’m Adam
Biotech use of restriction enzymes
GAATTC
CTTAAG
Sticky ends (complementary
single-stranded DNA tails)
GAATTC
CTTAAG
Restriction enzyme
cuts the DNA
AATTC
G
G
CTTAA
Add DNA from another
source cut with same
restriction enzyme
AATTC
G
G
AATTC
CTTAA G
DNA ligase
joins the strands.
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Recombinant DNA molecule
DNA
GAATTC
CTTAAG
Paste DNA
 Sticky ends allow:

H bonds between
complementary
bases to anneal
 Ligase

enzyme “seals”
strands
 bonds sugar-
phosphate bonds
 covalent bond of
DNA backbone
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Gel Electrophoresis
 Separation of DNA fragments by size

DNA is negatively charged
 moves toward + charge in electrical field

agarose gel
 “swimming through Jello”
 smaller fragments move faster
cut DNA with restriction enzymes
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Gel Electrophoresis
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Gel Electrophoresis
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Measuring fragment size
 compare bands to a known “standard”

usually lambda phage virus cut with HindIII
 nice range of sizes with a distinct pattern
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And from that comes a host of…
Biotech Tools
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