1. Quickie Intro to DNA Technologies

2. 1953 article in Nature
Watson and Crick

3. Double helix structure of DNA

4. 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

5. Discovery of restriction enzymes
Werner Arber
Daniel Nathans
Hamilton O. Smith
Restriction enzymes are named for the organism they come from:
EcoR1 = 1st restriction enzyme found in E. coli
Werner Arber discovered restriction enzymes. He postulated that these enzymes bind to DNA at specific sites containing recurring structural elements made up of specific basepair sequences.
Hamilton Smith verified Arber's hypothesis with a purified bacterial restriction enzyme and showed that this enzyme cuts DNA in the middle of a specific symmetrical sequence. Other restriction enzymes have similar properties, but different enzymes recognize different sequences. Ham Smith now works at Celera Genomics, the company who sequenced the human genome.
Dan Nathans pioneered the application of restriction enzymes to genetics. He demonstrated their use for the construction of genetic maps and developed and applied new methodology involving restriction enzymes to solve various problems in genetics.
Restriction enzyme movie

6. Restriction enzymes Madam I’m Adam Action of enzyme
cut DNA at specific sequences
restriction site
symmetrical “palindrome”
produces protruding ends
sticky ends
Many different enzymes
named after organism they are found in
EcoR1, HindIII, BamH1, Sma1
CTGAATTCCG
GACTTAAGGC 
CTG|AATTCCG
GACTTAA|GGC 

7. Biotech use of restriction enzymes
GAATTC
CTTAAG
DNA
Restriction enzyme
cuts the DNA
Sticky ends (complementary
single-stranded DNA tails)
AATTC G
AATTC G G
CTTAA G
CTTAA
Add DNA from another source cut with same restriction enzyme
AATTC G G
AATTC
CTTAA G
DNA ligase
joins the strands.
Recombinant DNA molecule
GAATTC
CTTAAG

8. Paste DNA Sticky ends allow: Ligase
H bonds between complementary bases to anneal
Ligase
enzyme “seals” strands
bonds sugar-phosphate bonds
covalent bond of DNA backbone

9. 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

10. Gel Electrophoresis

11. Gel Electrophoresis

13. Measuring fragment size
compare bands to a known “standard”
usually lambda phage virus cut with HindIII
nice range of sizes with a distinct pattern

14. And from that comes a host of…
Biotech Tools